Uh, Simon - YOU ALREADY CAN have 5 bonded packies on a non-tamer.
You can feed them, keep them in your house, and they will bond as normal.
My Archer/bowyer has 3 bonded packies AND the bonded horse he rides. One of the packies logs out with me, then logs back in with me. I've been running the character like this ever since I got the 6th character slot for the character (was it 8th or 9th anny box?). He used JOAT to retame 4 packies someone had released or had go wild, and 3 survived to bond, being logged out in the house like the pets from ML. The current system makes it even easier, as now they are autostabled if I log out with them empty.
Non-tamers need to have at least 3 slots, to allow crafters to more easily swap between fire beetles & giant beetles as needed for their duties, plus still have a normal packy, mount or golem, and the ability to go totally on foot for things like attending auctions and other player-run events (nothing is more annoying at an auction than having someone lose conn, they get booted out of the house on relog, BUT their pets end up standing on the seat the character was in when they lost conn).