I like the idea. Like everything else, it will never happen of course. It also has nine million different issues, question marks and integral little dysfunctionality here and there. ( What happens to economy? Would ppl close many extra accounts cause of this? How much not being able to sell Xfer tokens would lose money for them?" etc etc etc.
Ignoring all these, I still like the idea. Across all shards, you could have...Say, one house between sizes Castle-18 x 18. Two houses around 14x14, three houses of 8x8. Still only one/shard though. You could not have castles on ATL and Europa both on same account. You could have Castle on Europa, 8x8 on Atl, 14x14 on Great Lakes. I think it'd be fun. It will never happen of course.
Considering the current population, UO would need shard merges SO BADLY. We have one pretty busy shard where game feels reasonably alive. And dozen(s!) of shards anywhere between ' little tooo quiet' and 'completely dead.' Would be so much better to have two or three shards full of life. ((And if some half dead shard hero interjects here with
" but mah community!" I'll tear my eyes out I swear)) Regardless, Shard Merge is another thing that can and will never be done so hay.
Next best thing would be a " soft merge" where people can move between Shards with relative ease and freedom. Like Moongate that takes you from ATL to Europa. 100 hour cooldown. This way I could do group hugging on Europa, PvP on ATL, RP on Castskills and PvE on Origin. Struggling, small RP guild on Catskill would suddenly have, not just Catskill players but entire UO playerbase as potential recruitment pool. Same for a Champ guild on Origin. Your idea would help and support this " soft merge" taking place. I think this could be done. It will never happen of course.