Not many people are interested in MLP I guess, or at least not the ones with enough money to commission their own toy.

Multiple people have asked me to make these happen (and I'm sure others who have made customs before have been asked as well). Two reasons why they don't exist yet:
- One of each pony type (alicorn, unicorn, pegasi, and earth pony) is all that would be needed, plus a cost-effective means to print custom colors and cutie marks. If you think folks mad about poses were bad; this is a recipe for social disaster.
- The prevalence of folks wanting copyrighted characters; some folks who were possibly making 'too much money' at selling unlicensed MLP merch have been successfully shut down. That doesn't mean that it wouldn't be allowed; but it would be something that the creators would have to be ready to cease and desist on order from Hasbro.
- The only one I'd want to make is Gilda, because Gilda is best pony. ^^

I'm guessing all those terms just mean any combination of having or lacking wings and a horn?

Yup.

oh i would love to have one myself

It is a shame, I'd buy some up. My first over all pick has to be Dashie, then I'd go with Pinkie Pie, and Twilight Sparkle. I think for right now that'd be a lot of red tape to cut through to hammer out a deal between Lauren Faust/Hasbro and the inflatable companies. But I would love to see life sized custom ponies within the next 5 years.

I think the main reason is that people are worried about what Hasbro will do when they find out someone's using their IP without permission :P

They seem to have no issue with the plushes that people have made for themselves (and haven't gone after those who make commissions of such yet) but those are easier to make yourself if you know how to sew and such. Inflatables are a different matter given for the most part you do need a third party company to make such so I would tend to agree with you there, What I am surprised at is they haven't released a line of sea pony toy inflatables for the pool or such yet but then they haven't even put such in the show either (Just the comics and a few books).

Well, I've heard about a fursuit maker, who did several MLP suits, that he did get into trouble about it.

Ouch well they were rather public about it at fur cons and the like, I suppose it was a matter of time.

http://www.horse-news.net/2015/01/c.....nflatable.html