People have spoken about this on multiple occasions, so I'll try to explain this and what I think.
Yes the point of pico8 is it's limitations, noone can disagree with that. They have been selected to make the developement experience as fun as possible, and they are there to force developers to be creative. An example from something I'm working on is how I place enemies. I know that the token limit is getting closer to my throat for every line I write, so I needed to come up with a solution that would cost less tokens than the normal one. In my game I have enemies coming in waves. This cannot be randomized as that would make speedrunning very weird and unfair, and speedrunning is a big part of the game. My first though was to keep the what enemies comes when in a big fat list, but since there are quite a few of them I didn't want to use up my few precious tokens for that. What I did have was a lot of space on the map, so I used that instead to save the waves of enemies, and it was a really good compromise, but most importantly of all, it made me do something I wouldn't do normally. So that's the power of this limitation, it makes you think outside the box, and inside the cartridge. (Yes that was terrible I am deeply sorry).
I know there is a lot of people talking about the code limit, and that it is too small. And I agree with it being small, the limit is making it hard to make more complex games with. But is the point of pico really to make complex games? Or 3d engines? Or whatever? That's up to each and everyone, but I don't think you should be making such complex things. It's about being creative, not remaking doom, not making the next aaa title. And another thing, if the limits are starting to get less strict, then at some point the original idea of pico would be completely gone, as it is these limitations that makes the engine what it is.
Disregarding all that though, being able to make two cartridges and slap them together to use both of their memory would be really damn cool.