If I understand your parameter saving suggestion, then the Wersi OAS instruments have had it for years, in that a pre-set saves sections, and depending on the selection you choose to store in a pre-set it will save all these selections, however if you don’t choose to save any particular section then this will revert to the global settings. (Each parameter can also be left at a standard setting before saving if required)

Some of the more advanced features you requested (Multiple fills for example) while ideal for Pros, would confuse most home players completely, (About 95% of arrangers are sold into the home market, which is what manufactures have always designed them for) so while it could be done, sales wise it is probably not in the manufactures interest. (A module on the other hand is a completely different kettle of fish)

Bill