It might be slightly easier given the assumption that you only want to scan leaf tuples.
But there's an additional problem I didn't think of before. Currently we optimize index scans by copying all relevant tuples to local memory so we don't need to hold an index lock for an extended time or spend a lot of time relocking and rechecking the index for changes. That wouldn't be possible if we needed to get visibility info from the page since we would need up-to-date information.
We should solve this issue in the same way, of how we proceed with the index only quals, in current index-only scans.
