Since the English league sides probably face a similar "problem", unless the "EPL u23" (if they have it) is a success, why not set up a league structure for them? That is, a way to give them challenges against talented / quality sides rather than Lowland league footballers? Set up a northern British league, and a southern one, and have play-off at the end of the season for the u23 championship title.
Our biggest problem under Walter and his followers was that we bought far too much "quality", and thus hardly ever gave any talented youngsters a real chance to progress. And IMHO, most young talents grow better by playing with equally talented "veterans" / first teamers. Lowry showed up quite brightly, yet we send him packing to Hearts rather than keeping him, now he's essentially done. I have no idea what the problem with McCausland is, who was fully dumped after the arrival of Cerny. Probably more to do with Clement than McCausland himself. (Mind you, I'd put him in behind Cerny during such affairs like Sunday's or vs Dundee at home. No use having a RB there who fails to cover and hardly provides much these days bar consternation.) Mind you, we rather play Bajrami on the wing, or Hagi, than real wingers.
The problem remains the same as always. We don't rear truly talented youngsters in the way we should, back in the days of Walter because there was no necessity. Nowadays because of structural failure or ignorance on part of the managers.