OOO.. you like my mod yes? :D I'm excited to see you guys are testing it out.
I literally decided to call it Immersive Horses because I knew people would talk about it simply for using the term 'immersive'. Also, it was better than 'Improved Horse Overhaul', which was the original (crappy) name.
I'm actively working on the next major update, which I'm calling version 2.0 for simplicity, though not much will change. The next release is mostly bug fixes and generic changes for compatibility with other mods.
Followers riding horses or fighting on horseback will never be integrated into Immersive Horses because those features rely heavily on the follower's AI packages and/or scripting and that's out of scope for my mod. I don't want to be fighting follower mods for control over their followers. A dedicated follower mod could do a better job with it anyway.
As far as scripting goes, I guess you just have to take a scripter's word for it because it depends entirely on what the scripts are doing, not necessarily how many or how complex they are. What I can say is that the latest version of my mod doesn't use any OnUpdate loops at all and I don't use the cloaking method to apply scripts to horses dynamically either - instead the scripts attach at the race level for horses. The entire mod runs on a few thousand lines of code, which is a fraction of the size of the scripts for Convenient Horses and yet it delivers a similar feature set.
I hear from my users that switching from Convenient Horses to Immersive Horses mid-save is possible... but I wouldn't recommend it unless you really know what you're doing and you feel you absolutely must. I imagine a script cleaner would be necessary to really nuke out the CH scripts, then you may need to kill some or all of your horses or use console commands to force them to respawn to recycle AI, stats, factions, etc. Possibly other things I can't think of right now.
Anyhoo... let me know if you guys find any bugs or have any ideas for improvement. :)