Taking out a loan seems to be a reasonable proposition if the interest rate stays low, or the interest rate is fixed, you have some degree of "performance protection" and you are on a programme with an offer of a job at the end. However, without the above I'd say it's a pretty big risk.
Of course, the commercial aviation industry is very fluid, especially with these training programmes. In early 2011, no candidates could have forecast the BA FPP emerging, nor could anyone have forecast in 2014 that Aer Lingus would announce the following year that their cadet programme would be fully paid for. Of course, things can go the other way too but I gain the impression that in order to succeed in this industry you do have to be able to grab the right opportunity at the right time.