It seems that you are basically requesting something like a more permanent kind of SP cost reducer that you can activate beforehand, and also small chance to recoup costs of a spell when you are skilled (obviously, should scale with the initial manacost to begin with).
It sounds like a good idea. Solo mages wouldn't benefit too much, since they go for hit-and-run rather than endurance. But it would certainly boost mage's role for parties, at least for ones below lv50 where they can take another sub for utility. Only other way is to load up on lots and lots of SP potions or maybe tune up Meditation (what a concept!) etc. I look forward to the day where I could actually use Missile in party with deftank.
For other stuffs: "Essence of true ritual" skillhelp says that it "eliminates some minor parts of spellcasting" which are not important. So I think it would only really apply to casting speed. Make new skill if crit chance, stun, damage, special, pierce, blaah are wanted...or maybe tune existing things like Find weakness, Target focusing, Combat analysis to help this. I know that they already work for mages as passives, but if they were made active channeltype things like you suggest for true ritual...it is an idea.
Only bad thing I can see is that perhaps this would consume mage's EPs, and they don't have much of those
Oh yes, and some sort of target practice range for mages would be welcome addition, especially for casual players (anyone remembers dart throwing at Pink Bunny?). Library is perfect location. Although it would be bad if you summoned magical cloud and WHOOOPS! kill newbie talking to Aquail.