I am hesitant to tax witnesses to support development, although I am not certain that it is inappropriate either. Witnesses are somewhat akin to national defense metaphorically, as they are the mechanism that secures the blockchain against threats, foreign and domestic. Not only does taxing witnesses potentially obscure the impact of witness funding on blockchain security, and thus make it more difficult to effect security, but witnesses have demonstrable vested interest in certain types of development, and any financial incentive to compromise security for profit should be avoided at all costs.

Considerable funding is appropriated witnesses, and there should remain a stark and immutable separation between that funding and funding for development. Insofar as witnesses have stake, they also are taxed via their posts, comments, and votes, proportionally to the rest of the community. Further taxing our defense mechanism not only engenders the aforementioned hazards, but will effectively decrease the actual motivation provided them to effect our mutual defense.

Neither increasing the potential profitability of various developments to them non-proportionally, nor disincetivizing effecting the defense of the blockchain are acceptable proposals to me, although there is no reason to not consider witness rewards separately from funding development. As you may feel (as your comment seems to indicate) that witnesses are rewarded out of proportion to their contribution to the blockchain, such discussion may be appropriate.

Confusing development and security funding will not make such considerations easier.