I was surprised to see that apparently changing the mining subsidy in bitcoin is not completely ruled out, as long as the number of coins is not changed. According to https://en.bitcoin.it/wiki/Prohibited_changes this can be done with a notice period and sufficient miner support. (At least according to the authors of that page -- not all would necessarily agree.)

I see some logic in that, after all if you keep the number of coins constant then more inflation now must carry with it the prospect of less inflation later. This is self-limiting and self-adjusting over a long enough period at least.

So maybe if there is a good enough reason, just go ahead and change it?