Not staying onsite, that's part of the issue, figuring out where to leave the car. Because the parks close at diff. times the express bus doesn't run an extra hour like the buses do. It's just another layer of figuring things out. It will be so much better when I know when my FP's will be and that won't be till 30 days out. Stop the Madness!
Just some facts
if you go to AK first and hope on the express bus, you will have to go thought security there any ways, I am guessing it will be after pandora opens, right now AK has a lot less security lines then MK they may open more up to help with the more people going there, I do not know. I do know that I only go to AK one day a trip sine this park seem to take the longest to get thought security, I may just be going at the wring time,
the you will need to get back to AK to get your car, you can take the regular bus back, Disney will not leave you stranded even if one park is closed you will always have a way to get to your car. It just may take some time.
MK since security is all spread out it is much faster now, I think with parking at the TTC the harder part to this option is not the security but getting to the park it self. after you get thought security it can take up to 30 minutes to get over, ( but if you just miss the exspress bus this to can take 30 minute + a 10 or so minute drive) one option you have at the TTC is take the resort monorail yes it dose stop at the resorts but if the line is long for the express and boats then this one might be faster,
something you may not have thought about you can walk to the polly and take the monorail form there ( and go thought security there too, and this really should not be bad at alll) I know people that use to do this and they said it was much faster I have never done this.
Also if you do go to AK look up the express bus service thread and see what time the bus will leave AK for MK it should be right ( but Disney can change it) and try to be there at this time ( 10 minutes early is what disney says)