Now, is it actually true that 'Summon Creature' creatures (from the Summon Creature type MGEF, not a script using PlaceAtMe) CAN'T be interacted with? If that's true I've got to modify the mod I've been working on so that I can give commands to my animal companions.
I am working on a D&D style Ranger/Druid Animal Companion mod that will add a whole bunch of other features, but the main idea is different summonable (once per day but permanent until they die or you sleep like in D&D) animal companions that come with you and you can command them to do different things like a follower might be commanded.
I've switched gears to working on a different portion of my mod (really cool stuff, maybe I'll be able to release a v0.5 soon) so haven't really tested if interacting with the summoned actor is possible. So, to get back on track, can you interact with a summoned creature?
Dunno. Interesting question though. I'm willing to bet that you can interact with them, as the horse (when I made a version using a typical summon type spell rather than using scripts) did have an interact button, but it didn't say ride. I think this is simply because you can't ride a horse you don't own. So, in short, I don't believe you should have a problem.