Sorry to sound like a harda$$. How I understand it is.. Trying to circumvent the law would make me an accessory..
Your never too old to go skirmishing.. Im 33..
On our airsoft site we have players your age... You dont have to run around like a lunatic, that's what the younger players are for..
PhilS does deact and milled parts. Buying parts is OK just assembling them into a Replica Imitation Firearm is illegal. Since your not building a realworld weapon you might be OK. This is a real grey area, until somebody gets prosecuted there no precidents which is why im erring on the side of caution..
Personally Id just go try some skirmishing. You never know, you might like it..
Alternatively if you dont need a firing one you could get a resin pulse rifle.
Spatcave.com or matsucorp.yuku.com both do extremely nice resin versions.
Get a light and sound kit in it, metal upgrades and It'll be amazing.