Let me ask you all. What specific spells are the essential spells you want to create?
I brought up the UESP wiki page for usefull spells. Offensive Spells.
OFFENSIVE SPELLS
Basicly a paralyze and attack with bound dagger, you could dualwield theese 2 with ease, you would lose the 100 fortify blade part tho.
Fortifies your marksman and agility to do more bow damage, this is essentially impossible in skyrim either way.
Damage on touch and invisability, could dualwield theese or atleast turn invisible right after you done spraying damage.
Basicly exploits fortify magica, with the same effect as last one, only if you use this your magica will never run out.
Weakness to fire... only high magnitude for shurt duration. Probably wont be this ultra cheap version of it in skyrim.
Damage and turn undead, dualwield....
Summon a monster and invisability, dualwield. Really, wont bother you that u cant use a sword while being invisable.
Area spell that drains health and weakness to magic to be followed up by an area damage spell for cheap kills.
Drain fatigue and invisability (anyone else seeing invisability all over the place) knocks a target unconcious to make him easy prey.
Drain health for a cost effective kill plus soul trap, could be raccomplished by simply soul trapping and killing in whatever way u want.
Paralyze and damage, simply paralyze then do damage, you dont even have to change equiped spell if you use both hands.
Same only on touch
Calm and absorb health, basicly taking advantage of calm spell to make target oblivious to the fact you're stealing its health.
I find most of theese "Usefull Spells" to either be cheaper ways of doing damage then normally or ways of doing damage while not risking taking any yourself. Some of theese practicly break the game if you wouldn't run out of magica, but theres even 1 that prevents you from that! Others are fine, anyways most of theese could be possible by dualwielding as they rarely combine more then 2 spell effects
DEFENSIVE SPELLS
Drain speed, enemy can't see you if their speed is 0. One the edge of thinking this is an abuse... and speed isn't even in skyrim
Makes enemies non hostile and makes you invisable so you can sneak attack again. Possible to do this by using command and invisability dualwielded...
Light Detect life and invisability... can combine 2 out of 3, light might be with a set duration so use that before changing to detect life...
Invisability and heal, impossible in skyrim probably... if casting heal still makes you visable.
Still invisability being the main contributor. There is also alot of other spells that fortify your skills for few seconds which i will not adress.
I don't know, most of theese seem possible to recreate to some degree without spell making, all spell making would do in most cases is save you from using 2 hands or swaping spell. So it's really a question of convieniance. Anyone wanna show me a specific spell that really needs spell making and is key to your gameplay. Might be one i listed allready just give a reason why it/they are so important.