For some reason I woke up early Christmas morning thinking about this. (There have been several previous threads, which I am too lazy to find and link.) Some fairly easy ways to improve the deck builder and save system: Iventory shows item counts instead of multiple images. "Sell Excess" button when in shops (sells all but 12 of each Arcane Item, 9 of Weapon and Divine Item, 6 of Staff and Divine Weapon, 3 of everything else, doesn't sell Treasures). Allow figure changes in deck builder (use same buttons as in tavern). Have the "Remove From Party" button automatically unequip all items. When this change is implemented, run a script to unequip all items from inactive chars. Make inactive roster a list instead of char sheets, with scrollbar if needed. Show Portrait, Name, Race, Class, and Level; sortable by each column. Allow players to remove all their active party members. Have the Card Hunter Certifier (CHC) require at least one active char. (Already implemented?) Use CHC in MP as well as SP. (Already implemented?) Only have CHC open deck builder if party is invalid or a char is completely naked. (Right now it opens deck builder whenever your chars are de-leveled, even if all their items are legal.) Have CHC verify Peasant/League builds. (If Peasant gets official in-game support.) Keep the current party save slots (chars and items, 6 SP + 6 MP), but make all 12 available in SP and MP. Rename "Store/Retrieve" button to "Load/Save Party". Add 6 "Kit" save slots for each class, with "Load/Save Kit" button on char sheets, and available when in the middle of a module. If you load a Kit from a different race, don't load the Race Skill item. Also don't load items if their slot isn't unlocked on the current char. Use CHC after loading a Party or Kit to check everything is legal. (Optional) Use CHC before loading to flag Parties and Kits that will need tweaking to fit restrictions. It won't prevent you from loading flagged builds.
Since all MP chars are leveled up to 18, you'd load up your SP char with items you can't equip yet if he/she is not that level in SP yet. I would assume this is why the two are separate. I'd just be happy if we get more save slots, especially for SP (... as players have asked for many times before)