Long story short, we have some 2-wire BX running meandering circuits in our house to the lights and a few outlets (like 3 in the whole house) with no rhyme or reason. Should I make it a priority to replace the BX?

We replaced it in the 2 rooms we gutted, and when giving a room outlets I run a new cable and even try to move existing outlets from the BX to that new run, but should I try to rip it out other places like the lights? Or is it fine as is?

(Note: it is a post and beam house, crumbly horse hair plaster, no attic, and the base board is pinned down by two thick layers of wood flooring and gargantuan cut nails. Almost every project is a mini nightmare.)

I thought about putting a few of the lights on the outlet circuit, but I recall hearing that is bad form. Yet running a second circuit for just 1 or 2 light bulbs seems wasteful.