MP5 is a V2 gearbox (shares the same gearbox as the M4/16) as well so that's an option for internals. External wise not too many things are made that I've seen just a basic rail system and your standard attachments including rail covers, flashlights and PEQ boxes.
AK is good as well, it's a V3 mechbox and pretty common as well so internal upgrades are easy to come by. BUT A lot of people who try the "tacticool" AK look make it look bad IMO. I've seen a few "tacticool" AK's that I like but a lot of ones that I've seen I think are ugly as hell.
Also note silencers don't actually work at all. They're mostly just for show and to hide extra long inner barrels. They do suppress some sound but most of the noise is coming from the gearbox/motor area.
Read the FAQ's and you'll see a list of items that aren't prohibited from import, basically a lot of the items you want can be imported (guns and metal bodies are a definite no no but most accessories are fine, as well silencers are a grey area and although shouldn't be seized sometimes do).
ಠ_ಠLess QQ more Pew Pew
READY TO >> RACE