Timing split import would not be easy. It needs some kind of unique identifier from all timing services so one 'jane smith' doesn't collect all the race times for all Jane smiths. There are other details to work out.
Someone enters splits manually, by lap. Then coaches can comment per athlete. You should be able to compare times with some kind of factor for course difficulty to make the performance more comparable. That's no problem.
I can write it as a website. As long as you kept giving me feedback it would be no problem. It will be more time consuming and not immediately useful to you. If you stuck with it, I'd do it for free to you.
It probably wouldn't be ready for this season. If you are still interested, post an email to reach you.
Anyone else with any wish list features, post them. I'll see what I can do.