Well, as a trainer for a living... this is my take.
First off, if you want to be active in the training process, that's awesome. I teach your horse, and teach you how I teach your horse, so you know HOW he's trained when he gets back home.
However, you are sending the horse to ME, to get broke. I'd have no problem with the owner being there so long as every second I don't hear "Oh, don't do that, that's too mean!" or "Oh, you can't do that" or "You shouldn't do that to him" Or...
I'd get VERY annoyed if a client started telling me how or how not to do my job.
However, I could definately see some trainers charging to train the horse, and charging you extra for the lessons on HOW they do it afterwards. The horse industry is mostly based on money, after all.
But, if you're a good horse owner and want to learn the ins and outs, that's a-okay with me.