I'm not trying to fight either, what I'm unclear on are the specifics of the fix.
If they don't sell, no capital gains are realized, so what do you tax?
I'm not going to be able to comment on that with any confidence.
(And, yes, of course: establish a sensible annual exclusion, so no one accuses me of trying to demolish second mortgages for middle-class families, or whatever.)
What (good-faith) second-order drawbacks might this have? I'm genuinely curious about whether this would be a feasible idea.