I fiddled a bit with the .js files and implemented a workaround. Now you can keep your old savegames with only 30 slots in the collection. This works by refreshing the collection and enabling every single collectable each time you open the gallery. The downside is you miss out on the thrill of collecting them yourself.
Further i increased the save game limit from 20 to 99 (dunno if there is any limit by rpgm, could possibly be increased further by editing ".\www\js\rpg_managers.js" in line 333) and included my saves in the attached archive.
- Savegame #97 is you controlling Mia in her room and should enable you do most of the sidequests (interact with tablet on nightstand, teddybear and her laptop. the last one can be done multiple times).
- Savegame #98 is you controlling MC with - i think - every clothing bought and enough gold in the bank if i missed any. This should enable you to do the other sidequests. The one in the pool with the onepiece is still bugged.
To "install" this archive it should be sufficient to extract the attached archive in the root folder of "Living with Mia" (the one with the .exe).
If you don't want to use my saves just extract the data located in .\www\js and replace your files with it.
Hope this helps anyone. Have fun