Is there a way to set delivery priorities? Or some other way how I can make sure that certain stations are supplied first?

I'd be interested in beta'ing this mod if it evaluated the priorities on stations when leaving a provider station, instead of LTN's approach that locks the schedule in when the train leaves the depot.

Now you can set an implicit priority for request stations, if you set the minimum slightly less than the others. Among the supply stations, the one that will give the most resources is selected. And among several equals, the closest one is selected.

I want to move away from that to a more even distribution. Because in some cases, resources may not come to some request station at all - everyone goes to a higher priority one. I'm still thinking about the mechanism and interface.

Priority on supply stations is kind of important to have too. Like if you have a mine that you really wanna clear out first, or if you have a slow trickle of endless resources that you would like to use up first before accessing finite ones - such as core mining in Space Exploration mod. I do prefer LTN's way of having priority as a separate value. I find it that even distribution isn't really an issue unless your production really doesn't keep up with your consumption.

I've been thinking about this all night. I agree. The usual priority for supply stations will do and it's clear how to do it. And how to make the priority of the request stations is not yet clear - I'll think about it again.
I will try to make priorities for supply stations in the near future.

Request stations also need priority for mods like Nullius, where a lot of processes create byproducts. Byproducts need to go to useful manufacturing stations first, and only when production is satisfied (not requesting any more byproduct), then the overflow needs to go to disposal.