Why not just have the server handle all it's transactions in a database which can be handled without involving bitcoin or blockchains at all?
Then only deposit or withdrawl of coins will "spam" the blockchain.
Then only deposit or withdrawl of coins will "spam" the blockchain.
It's also worth mentioning a sidechain or payment channels can be "flushed" to the Bitcoin Blockchain (syncing up the balances of off-chain debits and credits) and this is not a trivial operation. If there is a community effort to a robust solution to this problem that other virtual worlds can also implement and inter-operate, makes total sense for us to test it and support it.
Blockchains are cool because they solve the problem of a global ledger without centralised trust. If the problem you're solving does not require the lack of centralised trust, it's just a really complicated and resource-heavy way to implement a balance database.