Im interested in contributing to making this happen. It would be great to create a module that supports more data into the page module. Something like a page builder of some sorts. I think starting simple with the intention of making the ability to add multiple "content" sections and reordering of those sections and have it stored in a separate database (as to not mess with migrations for any core page updates).
My original thought was to just tie into the events system and have the "content" field be adjusted to be stored as an array of "contents" sections. But as you said, migrations and poor handling of data could cause that to get messy.
Either way, I'm interested in helping. I might have a few questions to help with direction to adhere to your view of best practices for developing for pagekit.
How do we connect? Here?