That dichotomy is the problem the OP is proposing to solve. Ideally, it would be possible to use the limited on-board memory to hold DynaCabs of your choosing, instead of using the process of shrinking the Dynacabs-but-not-really-Dynacabs down to an IR in CabLab.
This wish has been discussed at length before, but the point is it's a lot more convenient to work with a Dynacab in the cab block editor than in CabLab. (and yes, it would be nice if the on-board Dynacabs had the extra features found in the packs.).