The big problems with this suggestion:
Magic doesn't scale with the game in
WHFB. You may suggest the cap of
2d6 dice is a good thing because it makes magic less spammable, but it means a 1,500pt army with one level one Wizard has about as many power dice as a 3,000pt army with ten wizard levels spread across four casters, which is irrational and punishing for no good reason. (I wouldn't be at all surprised if the Psychic phase in 7e was a testbed for rewriting power dice allocation in
WHFB 8e to scale)
There are no magic-less factions in
WHFB. Necrons, Tau, and whatever "we don't like psykers" Space Marine factions you have to deal with in
40k are all well and good when the psychic phase isn't particularly important, when it becomes a core part of the game in
WHFB every single army needs to be able to do things in the Magic phase. The only magic-less faction is the Dwarves, who nevertheless have magic-like stuff and do things with dispel dice. Leaving mages out of your list both prevents you from actually using any of the items that mess with the Magic phase, by the way, and magic can seriously ruin your day in a way that psychic powers can't; I suggest you go back and read through
WHFB more carefully. Pay special attention to Dwellers and remember that 8e favours infantry hordes.
The suggestion of items that mess with the psychic phase isn't a bad one (see
http://www.dakkadakka.com/dakkaforum/posts/list/597715.page for more discussion on the subject) but up and replacing the psychic phase wholesale with the Magic phase as you suggest would...let's see...make the psychic phase more or less valuable depending on the size of the game and make casting and dispelling more reliable. Not sure that's quite what you were aiming for.