If this is what you want to do, just be aware that then you CANNOT move to Universal hotels for your non-WDW days. You need to have a valid ticket (your AP), PLUS be on WDW property (your room key) to use EMH... the AP alone will not do it...======================
I would really want to be able to use EMH even if I visit an off-site park that day.
I know Universal and sea world usually close at about 6-7 max during the low season
so I will have time to get back to MK or EPCOT for some EMH the same evening.
This is where hopper ticket or annual pass comes very handy.
As a practical aside, after a full day at any park, even a day that ends "early", I'm not sure if you will have the energy to hop back to WDW, especially since you are going for so many days... you might have to treat it more as a marathon, less like a sprint... that might be a nice time to chill at the resort, go to the pool, even go to DTD for a while - none of which will require the AP...