All valid points, except that you and I have the luxury of being in a small nation where not every single league game is competitive. So two things are possible.
1. You play your guy at PG in a game where it won't hurt you too much. Early in the season you have cup games. Throughout the season you have games against newly promoted teams or weaker teams. You choose those weeks to train your guys in off-position skills.
2. You play with lower GS than you would want.
If you only have five guys then this is problematic. I have a very strong (for my league) second five, so I can get by using my starters as subs for
one league game a week. I also don't have too many problems with minute management. For me, minute management is one of the biggest differences between managers. Having stamina that is too high can hurt you here.
3. You look for trainees that are oddballs from the start. The6'11" pg with 6 OD and 6 PA. He will never be a triple 16 C because he usually has horrific big skills but you can get him to a serviceable level. Or the 6'0" C with 7 ID and REB to start.
How long has cross-training been around? I have only had one CT pop and it was in ID for a PG so I was happy. Do you experience on a regular or even infrequent basis? Does anybody? I have forgotten about it because I never get any pops form it. Well, I did get the one...
Once I scored a basket that still makes me laugh.