Couple things to consider and discuss.
- That would require a hard fork.
- Block reward is currently 1 TX. 0.5 TX for block finder and 0.5 TX for masternode. Would 10% come from finder or masternode or 5% from each?
- Also, there are other ways to establish a fund if needed.
Also, there is the question of. Who would be in charge of the fund? That would need to be hashed out. But before that happens we should wait on response from Infernoman. He's been the lead dev for a while now. He's still around.
As long as it's a multi-sig address and we as a community need to approve who holds the keys to that address. Also, i think it would be a good idea if the developer fee is 'opt-out'. So by default 10% will go to developer fund but if node owner wishes they can 'opt-out' of this.