BitShares Toolkit isn't built on Bitcoin code. The code was written from scratch and is the first to implement Delegated Proof of Stake as a consensus algo. You are correct that it aims to be a fully fledged community / ecosystem rather than a minimal base implementation of a blockchain ledger. There is actually a project called BitShares PLAY (
http://www.bitsuperlab.com/pdf/BitSharesPlayWhitePaper.pdf) that is in development which aims to be a decentralized game asset marketplace. Could possibly fit your use case well.
I see now. Bitshares-PTS was surrogate for initial development, and the DAC toolkit indeed seems to implement DPOS chain from scratch. Is it in useable state? Also, is it possible to use it without PTS?
The DAC looks a bit cowboyish and complex, however it indeed appears to be its own thing, mentioned in OP.
if you are merely looking to use a crypto token for an in game currency, I would suggest looking into user issued asset solutions. NXT, CounterParty, and BitShares all allow you to register user issued assets which you can then distribute to accounts on each respective blockchain.
That's indeed the idea, but the point is having the most lightweight client as possible (I'd prefer to avoid SPV, but in the end it might come down to that).