Lets start with alchemy- using reverse pickpocket paralysis potions to get free gold:
1- is bordering major exploitive
2- requires no investment in alchemy, paralysis potions being everywhere and commonly available
Frenzy potions- again reverse pickpocket-
Fwhat are you frenzying? You talk about being able to use it to kill anybody- i assume you mean neutral npcs by this. The stock unperked and unimproved frenzy also does this- silent casting from the illusion tree (very important for a stealth build that casts btw) will give this same option, and finally frenzy potions are again commonly available. This doesnt require perks or alchemy investment.
Fortify carry weight/fortify anything, common, buyable, and no investment in alchemy needed.
^this is a problem. I wish potions were not so common and alchemy was needed more

On to the illusion:
If you read earlier, i offer the left side of sneak tree is replaceable with illusion.
Muffle > stealth perk to silence armor
Invisibility > shadow warrior
5 perks saved. 7 perks in illusion to get silenr casting/expert casting.
I dont care about calm or frenzy or fury on illusion spells, wasnt arguing for those (skooma brought that up during his misread) 2 illusion spells perked i argue can stand in for sneak. From there it is true you are deep into illusion, so you totally could go all the way from there.
Clairvoyance- i dont care/argue about this.
And on a note about invisibility on cast vs potions:
You never run out of casts and have to restock, you will be amazed how often you can use it when it is unlimited, and the advantages it brings.
If you havent tried it, and since you argue potions are just as good- ill assume you havent. I suggest trying it.