I know it would personally help me quite a bit, as I'm always missing when the cursor changes. I'll click early before I have a target cursor, assume the spell is going off, then try to cast another spell only to realize I've messed everything up. A little more visual feedback would do UO's magic system wonders IMO. Things that are taken for granted in modern MMO's such as cool-down tickers over spell icons, spell icons going red when out of range, visual circles for area of effect spells so you can see exactly what you're targeting, and a casting bar letting you know when your cast is interrupted/complete....All of these things would be amazing.
I know I've read somewhere that Pinco looked into doing a visual circle around the character to show the range of certain spells, and he said it was impossible due to him not being able to read the "zoom" setting....But how about the other things mentioned here?