Just an update. I figured how to make things work with just eventing!
So, I first tried it out after leaving the stairs as purely impassible. Didn't work.
That might have been because of theplugins I"m using from Visustella which allow for diagonal moevement already or for some other reason...
Anyway, I made it work by tweaking the passability a bit on the top and center tiles of each dierection of the diagonal stairs.
Again, I'm not sure why that mattered, but that's how I made it so that eventing diagonal movement worked as intended. I mean, I could just go up as is but I wanted the practice.
Going up was a simple enough affair with copy and paste, but going down was required me to adjust the route a tad on each event.
Still, I got it to work just fine and it's great practice for short steps and eventing in general.
Either way, thanks for pointing me in the right direction!