I wouldn't worry about Speechcraft. I have chosen it as a USED major, and it still moves slowly. Do not play the mini-game with everyone you meet, just chat with most people. You can also avoid Speechcraft by using Illusion Charm spells.
Here's my two septims, after having run many different types of mages:
I agree with glargg.
Choose the skills you plan to use. Drop Alchemy to a minor, always.
I currently have an Altmer Apprentice in addition to a warrior.
The Altmer is a good example, as he was designed with severe limitations.
His strength and endurance are still the same as it was when he started. Endurance is like 35. Which means he is a one shot kill. Strength is whatever it is, 40 I think, which means he can only carry about 50 pounds beyond his traveling kit. He uses three majors only, the rest are unused.
Destruction
Illusion
Conjuration
Using only three majors, means he stops leveling at level 20. He has supreme magicka power, and even though he is a one-shot kill to most all other spellcasters, he has many ways of dealing with them.
All three of his majors are now at 100, heck, he doesn't even carry a weapon anymore... bound dagger for 50 seconds is enough. My mage heavily uses custom spells.
With an Endurance of 100, I think you should have no problem.
Choose the skills you plan to use, then use them. You need your magic skills to be viable killing skills from the get go.
I am doing a four majors melee warrior right now, where what you propose would be quite viable, as I am heavily restricting his magic usage, however, I believe you should choose magic skills as majors for a mage.
Good luck!