Another consideration is ... say we decide it didn't work out in the real world and doesn't see enough use, has needed more maintenance than expected, etc. Unlikely IMO but allow that for the sake of argument.
Well... this is something we can rip out.
It's not something that'll deeply and permanently change fundamentals of the on-disk heap representation. It doesn't add new data types we can't easily remove. It's... just not that intrusive. Especially from a UI/application PoV.
So our *risk* here isn't that great either. Our commitment doesn't have to be total. There aren't semantic differences that we will break apps by undoing if we decided to change how they worked behind the scenes, drop the idea entirely, etc.
Sure, we'll have them in supported releases for a while even in the VERY unlikely event that happens. But it's not like there's much code churn there, much cost to a little used feature.
All that said, I'm far from convinced this will be niche or little used. Nor does it look hugely intrusive or likely to be a maintenance burden. So the cost side of the cost/benefit/risk analysis isn't exactly overwhelming.