East Yorks under fire in Normandy.. not a small pack to be seen.
You also need to look at pics of Brit airborne in the field at Arnhem.
Everything from full kit to just a belt and an ammo bandolier.
The scale of issue in the manual goes out the window in the field.
Even with line inf, you're unlikely to take your small pack out with you on a recce or fighting patrol, quite often just ammunition and water.
In reality when the merde hits the fan, most lads would ditch the encumbering stuff until the firefight was over.
http://1.bp.blogspot.com/_JPq6z25JOog/R ... /house.jpg
http://wwii.ca/photos/netherlands/arnhe ... pr45_2.jpg
http://www.ww2incolor.com/d/225333-2/Br ... +at+Arnhem
"I think we are in rats' alley - Where the dead men lost their bones."
East Yorks under fire in Normandy.. not a small pack to be seen.
You also need to look at pics of Brit airborne in the field at Arnhem.
Everything from full kit to just a belt and an ammo bandolier.
The scale of issue in the manual goes out the window in the field.
Even with line inf, you're unlikely to take your small pack out with you on a recce or fighting patrol, quite often just ammunition and water.
In reality when the merde hits the fan, most lads would ditch the encumbering stuff until the firefight was over.
http://1.bp.blogspot.com/_JPq6z25JOog/R ... /house.jpg
http://wwii.ca/photos/netherlands/arnhe ... pr45_2.jpg
http://www.ww2incolor.com/d/225333-2/Br ... +at+Arnhem
Keep looking Comrade, and you will find all the pictures you wish, these Chaps you have Imaged are not about to Assault the Enemy, by the looks of them... more like watching a Strike, however if you wish to have a cupper after the "Snork" you will need your Small Pack. In a Battle of Movement you can't go back for your stuff, you will need your Small Pack, all Combat training is done in Fighting Order.
As you wrote you always adjust your Personal Equipment to suit your Combat Mission and you never see a Soldier carrying anything more than be needs to.
But it is best keep your gear to hand, you might need it..
If i could be bothered i could drag out as many pic of guys without small packs in combat as those that do
Having *been* an Infantryman i can tell you that when you need to move and fight you ditch everything you dont need to in your harbur area or on unit transposrt and go back for it later, veterans accounts are numerous of men sepearated from their pack for some time.
The armys maxim has always been Live with whats in your pack and fight with whats on your webbing (and in recent years 'survive with whats in your pockets' but that parts Post war lessons learnt in E&E)
The point is still valid, a small pack is clearly not essential for a combat infantry basic impression.
I've making this statement on over 20 years of researching WWII British Infantry, i doubt the OP wanted to do a impression of a recruit in training, he simply asked what the most basic webbing set up he needed to *game* was.
"what kit would be reccomended for airsofting,"
Was what the OP wanted to know and to be fair i think the answer of belt, cross straps, water bottle and cradle and 2 basic pouches is a pretty fair answer.
Just trying to answer the lads actual question 
"I think we are in rats' alley - Where the dead men lost their bones."
...I think the answer of belt, cross straps, water bottle and cradle and 2 basic pouches is a pretty fair answer.
We've been airsofting for the last three years with just the above and can confirm it is indeed all you need.
We do actually have small packs now but 99% of the time they get left in the car (motorpool?).
I've found this thread really useful. My kit requirements are based around what is useful for airsofting at open days, since I don't do re-enactment, so it's nice to read about what you guys have found to be useful, but historically accurate. I'm probably gonna add a small pack, but only because I wouldn't mind being able to carry a bottle of green gas (and a rain cape, which is not just useful, but necessary for airsofting in 3 out of 4 seasons in NZ).
Thanks, guys! 
Friends meet to part - love laughs at faith;
True foes, once met, are joined 'til death!