No. I'm going in April, if on a Saturday morning, MK didn't open till 1pm because of runners, I would go apoplectic on management. There is no need for a new solution here. The system works adequately as it is.
Do you blow a fuse when the MK closes at 7pm because of a special event? One that you may not know about at the time you book your trip...because the dates haven't been released yet.
I think @MickeyMomV has a great suggestion. Open the parks later - probably just MK - and close later...but don't make the late closing EMH. I've visited several times when the MK closes at midnight or 1am...and then EMH had extended my time on the park another few hours.
It would only be 4 Saturdays and 1 Sunday each year - the 5 days the halfs and full marathon are run.