The outright suggestion isn't as ridiculous as some ppl are making it out to be, but, in its present state, UO isn't set up to handle it well. Also I don't think it would succeed in the job you want.
One thing is that the way these shards have been set up balance-wise expect Fel to be there to create a degree of rarity of certain items, in particular the non-tradeskill power scrolls. If the same balance were to be maintained, the power scroll distribution system on that server would need to be different.
The game and item mechanics would not be different in this shard because, for sure, the ppl who make this game wouldn't want to basically create and balance 2 different games (RE: nerfing some abilities due to overperforming in PVP). If a PVP-related nerf to player abilities were to happen which genuinely damaged PVE's balance (talking theoretically, here), that's a dev shortfall sort of thing, and shouldn't hit either sort of shard.
I agree that lame behavior in chat should perhaps be caused to be segregated between Tram and Fel. WoW had an interesting solution in that there are no chat channels which exist server-wide (unless you create a channel of your own). UO server population seems a little low to do exactly the same, but, I could totally see Trade channel only being available in cities and while you are in a player house, and the help/general/whatever channels being tram and fel specific (assuming it's not like that now). Some people might whine about such a change to trade chat but oh well, they would survive.
If such a shard existed, its inherant differences might make it a bad candidate for transfers out.
So yeah ... I don't call the suggestion of a Tram-only server ridiculous. But there are some difficult-to-overcome balance type obsticles to it, and, the stupid chat etc. are perhaps better dealt with through a more appropriate arrangement of the existing server chat channels.
Just create a shard, remove Felucca entirely, let Ilshenar champs drop powerscrolls, and don't let anyone transfer off. Don't even worry about separate balance rules. Just make it UO minus Fel.
Very little codework and I'd bet all my gold that it would do 10x the population of Siege, sustained, easy. Since it would just be pulling people from other shards though, there isn't much point from a dev perspective.
I agree it would function, just not sure it would be a happy result in the end. Not saying it's ridiculous to try. Could be interesting. Just saying that it would end up kinda.... messed up and yeah, one shouldn't be able to transfer either direction IMO. It's not exactly fair/smart to offer to xfer an existing character into what amounts to an entrapping, black hole shard.