Viability of mod concept -- hireable "ostlers/grooms" who can mount your infantry (for strategic mobility, not battle)

[Maklodes]

Reposting from elsewhere: if this idea has already been discussed a lot, I probably missed it...

My basic idea: suppose that you could hire a guy who can manage basic sumpter horses, take care of them, and coach your foot soldiers on the basics of riding without ending up as a paraplegic? I think that mounted infantry is a pretty popular idea for M&B mods, but I'm not sure this particular mechanic has been proposed, or whether it would work.
Mechanics

• Ostlers could be recruited or trained somewhere. I'm inclined to say they can be recruited at a castle courtyard, since it seems like castles are pretty likely to have a good equestrian economy, and they seem like the least interesting locations so far (compared to villages and cities).
  
• Recruitment cost per ostler is about 40 denars. (Reasoning: you're getting a horse manager and about five sumpter horses. Five sumpter horses are worth a bit less (670 denars) than a medium quality warhorse such as a hunter (810 denars). Conversion of infantry to cavalry mounted on a hunter (e.g., Swadian footman to Swadian man-at-arms) costs about 40 denars. Why you can upgrade a foot soldier to have a 810 denar horse for 40 denars is a mystery, but that's the precedent...)
  
• Ostlers have a weekly wage of 30-15 denars. (Reasoning: minimum cost of horse maintenance is established at about 4-2 denars. (Example: Khergit skirmishers or Manhunters (9-5 denar wage) vs. other level 10 troops such as Nord footmen and Rhodok crossbowmen (5-3 denar wage).) Ostlers come with five sumpter horses (maintained at 20-10 denars) and have overall valuable skills (mostly non-combat) comparable to a mid-level soldier such as a Nord trained footman or Swadian skirmisher (10-5 denars), for a 30-15 denar total)
  
• In battle, Ostlers are like crappy basic infantry, although not quite recruits (equivalent to, say, Vaegir footman and such), with a basic spear and shield or something. However, their default AI is to hang back from the battle holding a bunch of sumpter horses. (Maybe they even automatically rout at the beginning of battle to keep them out of harm's way?)
  
• Each Ostler counts as cavalry for the purposes of movement, and also causes four of your other infantry to be counted as cavalry for the purposes of strategic movement. Thus, 10 Ostlers and 40 Rhodok foot soldiers would count as an all-cavalry army for strategic movement.

Anyway, I don't know much about modding, but do you think this would be moddable? Could the party speed calculations be modified to have a special type of party member modify what other party members count as?

[Veliky Kaiser Theos]

The Floris Mod Pack has similiar things, where having certain amounts of specific units increases your stat by one, such as having 1 scout increases pathfinding by 1, 20 by 2, 40 by 3, etc. Floris is open-source, you could take a look at how they did it.