I really like your ideas actually, especially the way you'd give viability to Spell/Skill Speed.
My two cents on the classes I main :

RDM
Dualcast not fading when you go into melee combo : that would be OP. Most of the time if you go 80/80 and have a dualcast, you want to use it to disbalance you mana and get a guaranteed proc on your verflare/verholy. While having a full combo, verholy/flare and verThunder/Aero all this squeezed in your best moments of Embolden... it's too much. And most of the time, you will be using the GCD of that second spell to move into melee range (by corps à corps or regular movement). A dualcast is never lost in that situation.
I like your idea of progressive Embolden, makes so much more sense to burst to have something going up rather than the other way around.
As an abstract addition, I'd love something to get Mana regen (as a bulk or a progressive ticking regen I don't mind), in the RDM kit. Maybe part of Embolden or something... And avoid the chain rez by making rez more expensive for RDM somehow I guess.

SMN
I'd actually hope that each pet actions can be weaved as oGCD, and not clumsily queued in that little Carbuncle's stubborn AI.

BRD
I'd add an aggro dump on that action that makes you jump back. Bards would be thankful.