Weather or not the pro sports model is a good thing to aspire to...I'll leave that up to debate but that's a reference point where this model works. It could be adopted with slight modifications.

The apprenticeship model also works decently well...at least I'm not consciously aware of many carpenters, bakers etc. job hopping once their education is complete.

But like I said the more optimistic view is that employees might actually like your company and that the principle of reciprocality works in this setting. There's going to be a subset of people who are going to be pretty happy that you cared about them and financed their education (and there should certainly be strong mentoring on the side not just "here's your money, call us when you graduate"). If someone just hops away...well that's expensive but might be less expensive than having such a person at your company. Fail early etc.

And I mean noone is forcing you to sign such a deal. If you want to argue evil employers and "wage slaves" (a term I personally think is fairly ridiculous, especially if applied in the context of IT jobs, but Chomsky gonna Chomsky) and say that starting your life with huge college debt isn't exactly going to set the workforce free either. You're pretty exploitable if you need to get rid of crippling debt.