Investors and debtors will want inflation.
Creditors and money holders will want deflation.
Even with demurrage, money holders will want their money to appreciate.
And yes miners will want more subsidy, even if it will be translated in more competition later (that neutralize their increased profits), that won't be instant, the increase in the subsidy would happen first.
I don't know, maybe it all get balanced as you say.
About the concrete voting system, I would suggest to define a reference currency and the people vote how higher or lower the chain currency is compared to the reference. And the system could ignore very extreme votes or the ones that are vey different from the rest.
But wait, miners can leave out the votes they don't like.
This decentralized price index problem is really hard.