Yeah, I don't do cartridges for the same reason as others: I change the ink often, and the selection with cartridges is almost non-existent (and much more expensive per ml).
For a lot of pens, there is no "locking". You just remove the cartridge/converter, and add silicone, and you're good to go. You can always revert back.
I ran carts only in my Vanishing Point(s) for years, but largely because it was easier for travel and I found the ink color and consistency very pleasant.
Once I stopped traveling so much I started using more bottled ink, which is fun, but then you get to a point where you have a mental matrix about which inks work best with which paper in which nibs…
For a lot of pens, there is no "locking". You just remove the cartridge/converter, and add silicone, and you're good to go. You can always revert back.