As you say its unlikely most of us have the skills necessary to carry out the mission in a truely stealty way so it would be better to used enemy uniforms and rely on disguises and bluff. The Allies can still attempt to do things stealthily but if that fails they have their disguises to fall back on. Of course if the allies do have to get close enough so that they can be recognised then it may take a degree of acting dumb on the sentry's part to get the desired result but thats all part of the roleplaying element needed to make a game like this work.
Due to the fact most of us know each other I think a possible way to add extra confusion for the Germans in the scenario and give the allies an edge would be to have the Germans not knowing who the Allies actually were. If everyone was dressed as Germans and only the Allied players knew who they were it would stop the German players from reacting to them as enemies, be it intentionally or not. The Germans would be split up into various groups on the day and assigned different roles and would only know that those in there immediate group, plus perhaps the officers in charge, were actual Germans. So when they encountered another group they would not know if they were truely friendly or not (& vice versa for the other group) so would have to regard them suspciously, incase they were allied but friendly & openly as they're more likely to German.
the players like me who dont have german uniforms can play the towns volksturm ,only need an arm band, weapons at a collection point untill the alarm sounds.........
Well I was still only thinking of basic uniforms for most of the allies so a borrowed greatcoat, belt & cap would be enough, although I'm sure a few of use have more than enough we can lend out. 
As you say though there is still plenty of potential for civilian or even milita roles.
Due to the fact most of us know each other I think a possible way to add extra confusion for the Germans in the scenario and give the allies an edge would be to have the Germans not knowing who the Allies actually were. If everyone was dressed as Germans and only the Allied players knew who they were it would stop the German players from reacting to them as enemies, be it intentionally or not. The Germans would be split up into various groups on the day and assigned different roles and would only know that those in there immediate group, plus perhaps the officers in charge, were actual Germans. So when they encountered another group they would not know if they were truely friendly or not (& vice versa for the other group) so would have to regard them suspciously, incase they were allied but friendly & openly as they're more likely to German.
Genius
Wait and see how the partisan rules at lightning work, you might be able to use the system.
"I think we are in rats' alley - Where the dead men lost their bones."
sounds great, like where eagles dare
the look of surprize when a german walks up and says "hello" before popping you with a silenced pistol 
we will need a bus, a fit blonde who can handle an mp40, and someone to knock up 6 fake focke wolf fighters 
"Take that you rotton helping of strawberry flan!"
Joseph Porta to "strawberrys and cream", in the sven hassel book ,ogpu prison
A good way of not knowing who the allies actualy are is when everyone books and sends their money they say in the paypal message which side they want or if they dont mind beign either but this isnt published on the forums then when the allied side is full it can be announced that no more allied bookings will be taken, but the player list wont be published so everyone books as normal eccept on the forums it will just say who has booked not who is a german and who isnt of course the british will be dressed volksturm/wermacht so the Falshy bodyguard will not susspect other flashy but there will be several groups of wermacht/volksturm patrols and they would be led off at the beggining of the game without being told who is german and who isnt so no one will know who of the wermacht is SAS and who isnt?
this could really work
hard to orginize, but doable
"Take that you rotton helping of strawberry flan!"
Joseph Porta to "strawberrys and cream", in the sven hassel book ,ogpu prison
another way to decied sides is to draw lots,then no-one knows till kickoff.
Well I was just thinking that if done at the Bryanks site the SAS would have to be fit enough to run around the hilly terrain unles you drew lots for those who feel they would be up to the task.
Yes that sort of booking is what I had in mind. People simply book to play the game but apply for a side (along with stating what kit they have) in private via PM, Paypal etc. Those who apply to play allied would have to be sure they're up to the challenge before hand but if there are too many applicants then they can either be drawn from a hat or selected by the organisers according to whoever they deem to be the best suited.
The rest are then assigned to the axis team and only told which group they are being put in on the day.
The selected allies can be briefed on their objectives in secret (& maybe have a hidden forum to discuss tactics) so they know in advance what they are required to do. Obviously it would require people to keep completely quiet about what side they were on to work as one German knowing one of their mates is an Ally could blow a who group's cover.
Sounds like there is a good chance for some Where Eagles Dare style tripple bluffs 
Well... interesting... but not really that realistic - a squad of Brits going around dressed as Germans. 
You've got nothing to ein, zwei, drei, vier
Yes its ludicous, who'd want to wear all that Jerry clobber.
Well... interesting... but not really that realistic - a squad of Brits going around dressed as Germans.
I had to read that twice before i laughed.
Nice one Andy.
First time round i was just about to list some historical precedent then the light dawned....
lol
"I think we are in rats' alley - Where the dead men lost their bones."
sounds great, like where eagles dare
the look of surprize when a german walks up and says "hello" before popping you with a silenced pistol
we will need a bus, a fit blonde who can handle an mp40, and someone to knock up 6 fake focke wolf fighters
with the dumb blondes i know, it would be less trouble to get 6 real FW 190's and make a fake blonde..................
"Take that you rotton helping of strawberry flan!"
Joseph Porta to "strawberrys and cream", in the sven hassel book ,ogpu prison
So, 12 months on...
Early war event? Check.
Normandy hedgerow game? Check.
Eastern front game soon? Check.
Norwegian heavy water plant game soon? Check!
Monte Cassino game planned? Check.
Kasserine Pass game planned? Check.
Jedburgh game planned (again)? Check.
It's been a great year, and next year looks like it's going to be just as good. Well done to all who have had the courage of their convictions to run games which are pushing the boundaries.
Ideas:
Norway
France 1940 (again!)
Crete
Barbarossa
Dieppe
El Alamien
Stalingrad
...
You've got nothing to ein, zwei, drei, vier
Barbarossa,Stalingrad
Want to see both of them and an Oosterbeek game SS vs Staffs or even Nunen or Nijmagen game done right so M43's gliderborne and airborne.
Barbarossa,Stalingrad
Want to see both of them and an Oosterbeek game SS vs Staffs
Oosterbeek will be done as a PBI game, hopefully next year, if all goes to plan.
Looks like its going to be a good year. 
I want to do an occupation game. German occupation troops against the resistance with civilians of mixed and often undecided loyalties. Resistance have to keep their identity hidden whilst building their forces and sabotaging the German war effort. Germans have to route out the hidden resistance and bring them down whilst protecting key assets. The civilians are there to confuse matters and assist whoever they see fit, according to their individual loyalties and aims.