I didn't claim anyone said it was stupid. But yes, I think the best balance is to have it running inside SFOS, alongside SFOS applications. A multiboot option would be another good alternative. But on a N900, if the OP wants to use it more as a mini computer than a phone, that could work too. It's not far from what PostmarketOS is doing based on Alpine.

The N900 can run DE inside chroot with Easydebian, I remember it worked decently some years ago, but some heavy apps or browser were pushing it a bit too far. I have never tried it with a tiling WM though.