Vote decay seems to me to be a no brainer situation.
Let's have witness votes be something that needs to done by active Steemians.

I'll weigh in on your last issue, that is, the possibility that witness stacking could occur

I thing the option to reduce votes to 16 (or less) is preferable to making the number of required witnesses for a quorum to be larger than 30 (31 or more)

Consensus is already difficult, and making it raised to 31 will only add to more delays, longer times between major updates.