I personally jumped in and got an M4 (I'm somewhere between 5'4" to 5'6", and also Asian so kinda thin...).
That was only because it was such a common gun to find parts for and because I got a great deal off the classifieds. Since almost everyone has an AR it's really easy to find spare parts and replacement parts right away, vs. having to order it internationally or waiting for it to get back in stock from being on backorder (most people don't want to carry large overheads so they try and limit how many of which item they have. They don't tend to not get as many parts for less common guns).
You could probably get an AR variant with a longer length, I'm thinking maybe an SPR.
Once you get AV'ed and you have a better idea of your height just lurk around the classifieds until you can find something you like/something you can get for a good deal, a good deal is important because you'll be spending a lot of money on the sport, be warned....
ಠ_ಠLess QQ more Pew Pew
READY TO >> RACE