I'm not sure I understand what are the instability problems...
The simple fact that there are more lost blocks and reorgs per se doesn't bring instability, at least if by instability you're talking about transaction confirmations. If the splits are honest, we can expect all transactions except coinbase to be on both sides of it. The confirmation speed will remain. And coinbase transactions normally take a long time to mature so they wouldn't be expendable before solving the split anyway. (right? or is it different here?)
Granted, there will be more losses to miners, but these losses will be the same to all of them. Well, not exactly, better connected miners would have better propagation, and in a way that's a good thing: you bring monetary incentives for miners to build up a faster network. Or even to evolve the protocol so that block propagation is faster (imagine how cool if Monero implements constant time propagation before Bitcoin :))
I don't think reducing space by having less coinbase transactions is a motivation for such a change. Coinbase transactions should be the least of your worries, if you expect Monero to grow.
Why is cryptonote more sensitive to reorgs? Is it because transactions might risk using a recent mixin which dies out in the reorg? How meaningful is the chance of this happening? And, if both chains have an identical copy at the same height of the transaction that creates your mixin option, is that even a problem at all?
I'm just questioning to understand why is such change wanted. Normally I'd be wary of changing important parameters like this unless really necessary.If it's just because you're concerned with a possibility that might never become true, I'd advice not changing right now. You can always hard-fork in the future if really needed.
Plus, faster confirmations are cool. :)