ideally, variation. like a small town sort surrounded by forest with bunkers through it with trenches etc. if you wanted really expensive then underground tunnels connecting bunkers to buildings, craters etc. modular walls in the town so the buildings can be changed a bit, and having some worn out furnishings so that its not just random empty rooms. also roads etc for tanks apcs to be usable, roofs accessible(and yet safe) guard towers. maby designed on the lines of an abandoned nazi town/refuelling station/outpost/prison camp sort of thing. smart planting so that parts of the site will change naturally in the seasons with undergrowth etc. well drained site though so that in bad weather the site dosent get churned up too much and the town bit being good enough tht it alone can be used in really bad weather. megaphones/speaker system all round the site so you have the option to play music, final whistle, battle effects etc. smoke machines for effects all over the site. burned out veichles including ex war ones etc certain amounts of lighting for night games(lights protected so they dont get shot out bud can be turned off?). themed buildings (such as bar, church, bank, police station etc) for improving theme of games etc. and maby for the marshals you know like the wee huts they have for guards that you can stand in and nothing more. some of those in key locations around the site that arnt in the way but allow them to view high trafficked areas(also keeps them out of your shot as well as making their job a bit more comfortable. maby depending on site accessibility (as far as how far from safe zone) a centrally located shop(in the village) for those so wishing to get bbs and drinks in between games(maby a form of voucher system so they dont have to carry cash on play areas?
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oh and while your at it to be perfect, how about parts designed like certain buildings/areas from history/ games( western style bar swing doors. or i rember form one f the original medal of honour games a night club thing with big vertical light signs which a sniper hid behind... fallout new Vegas styled town could be good...