See, this is the shame of it all Kat.
AoS item-centric stuff aside, were it not for the restrictive nature of Siege, I think it would have more players.
Ok, my connection to any of the American servers is poor generally (I'm talking 400m/s plus at the best of times...), that's not stopped my playing on other American servers. Although this pretty much kills the possibility of being able to compete effectively in PvP, it doesn't prevent me from other character templates.
The restriction of character numbers is the single biggest restriction for me.
If I want to focus then on crafter/gathering/trading templates, with all the skills available now, I would need at least a minimum of two characters, if not three, to cover all the skills I would want to use.
Yes, there's soulstones, but they're a poor answer and restrictive in how quickly you can transfer skills. I don't like the idea of having to purchase with real $$$, additional soulstones to take the quantity of skills I would need to store, not when I already pay a subscription to play. My opinion might differ there if UO was a FTP game. Likewise, I don't see why I should have to pay for an additional account, when I don't need to on other servers, where I can use five to seven character slots.
So personally, it's not the skill gain system, or AoS+ items particularly (although I don't like the over-bearing importance of items in gameplay...), it's character slots that's my main issue. Were it not for that, I would have already been playing Siege a long time ago.
There's lots of things I've enjoyed doing in UO over the years. I like to be able to do those things as and when I choose. That's not possible with only one character and that's arguably why Siege hasn't appealed to myself and many others.
If they changed just that one thing, I think you would soon see the population of Siege climb quite quickly.