Ultimately meaning Spellmaking as we've known it could not exist, because it wouldn't be the exact same.

First of all, a huge flaw in the Spellmaking design even in Morrowind and Oblivion was that it allowed you to bypass your actual skill level in a school of magic. Example of what I mean: if I am a Master of Illusion, but have never touched Destruction, I can go to a Spellmaking altar, and create a spell with as powerful of a Destruction effect as I want, just as long as the Illusion skill is higher, the spell counts as Illusion, and thus I can bypass my Destruction spell.

This becomes even worse in Skyrim where there is a perk investment to make skills good.

There also exists the fact that with the dual wield casting dynamic, and the fact that there are dual wield perks, how do these co-exist with created spells of multiple schools. If I have the Illusion dual wield perk, but not the Destruction dual wield perk, what happens when I combine a spell with Illusion and Destruction? Can I dual cast it? Well, then that allows me to bypass the Destruction dual wield perk. Am I not allowed to dual cast it? Well, that wastes my Illusion dual cast perk.

Then there's also the fact that spells this go round aren't as simplified as "target", "self", and "touch" - spells actually act differently now.

How does one combine a constant cast healing spell with a shield spell? Or a constant cast flame stream spell with a fury spell? Or a rune spell with a conjure spell?

Sure, there are lots of combinations that could happen, but lots that also won't work. And ultimately, to get it to work together, you would have to change Spellmaking away from something that it's always been.

I think the answer is the combined spells that we saw in the GameJam video. That's what I always thought the magic was going to be from the beginning, but it didn't end up that way.

Spellmaking can work, but it can't be what we've known it to be in the past of just virtually free reign over combining any type of spell effects together, because ultimately everything casts on self, on touch, or on target in a big ball of magicka.

Who cares if it's over-powered? Nobody is going to see it except for you.

The game is already broken. Right now it is broken for mages in ways that make it frustrating and dull endeavor. The worse thing that can happen if Bethesda gave us a system that could be abused is that magic would become on par with melee. I don't see the forum members with warrior characters clamoring for the removal of smithing, weapons scaling and passive damage boosts. I'm thinking the reason for that is because then melee would svck.

But that is what was done to magic.

Meh, I'm a mage, and magic doesn't svck for me.

iv already said there would be some restrictions in another post, stuff that just cannot mix simply wont mix

restrictons:
choosing a casting type effects every one of the effects (the effects will have area's of effect of their own though)
some spells would act differently under a different casting type (a summon rune could summon an unbound or a spray spell could have the effect of keeping the at arm's length while you let it kill whatever it wants) just like it should (and did, to an extent)
cannot duel cast unless you have all the needed perks (im suprised you didnt figure this one out, honestly, it is the one with the most simple solution)

see simple, i see no reason why spell making cant be included, it is easy to work out all the tiny kinks you mentioned

although, in the end, it is all up to bethesd to decide to put forth some effort to please some people