I'm not really sure what your intentions are here, honestly.

The ability to swap would be nice, of course, but since you can only do that on a level up, you'd probably not change your invocations much, if at all. I mean, a Wizard/Clerc/Druid can reasonably guess what they'll face on the adventuring day, so they choose spells accordingly. But guessing your needs for an entire level is just absurd, which means you'll likely stick to the generally-good invocations instead of getting something niche.

Warlocks do need some minor quality-of-life buffs, but I don't think this is it. Giving them an extra Cantrip and making the 1/long rest invocations (like Sculptor of Flesh) work without spending a spell would be closer, as Warlocks would now have access to some Long Rest resources for when they really need to nova.