The most important feeling while you play MMORPG game - feeling of your character progress. Currently we got pretty interesting 'skill scroll system' which gives possibility to gain all battle GMs in no time. It's fun to have it - so newbies could catch up with old players and go PvE/PvP almost right after they start to play. But we got a gap cause of it - not much feeling of RPG progression in long-term perspective.
But actully common 'power scroll system' which used at most modern shards isn't really change anything. People get 120' skills by macroing pretty fast and it still do not give certain feeling of progress. Macroing killing feeling of RPG in UO so I suggest different approach:
1) add possibility to gain skills past 100, up to 120.
2) the only way to be able to raise skill after 100.0 - to get special Ancient Skill Scroll; it's similar to http://www.cataclysmuo.com/features/scrolls , but gives only +0.1 skill per use.
3) This scroll could be found only at High lvl monsters (like dragons, deamons & etc) with quite low ratio, like 1:5; also could be found at treasure chests and some other activities
4) Make this scroll stealable/lootable for more fun

What it would give us?
1) almost endless character progression (you would need 200 ancient scrolls to max one skill; it's killing ~1000 dragons).
2) newbie friendly system stay the same (you get all 100 skills pretty fast with current 'Skill Scroll system'). Difference between 100 and 120 skill efficency (spell damage & etc) not really much, you could kill all end-game monsters and be successful in PvP with 100 skill.
3) it motivates players to hunt in deep dungeons and give awesome feeling of true RPG game.