I always thought it would be cool to have an XLR instrument cable with the ability to provide phantom power to active electronics. No idea if this is feasible or not, guessing not, since as Aged Horse pointed out: if it doesn't exist there's probably a reason.
Relatively straightforward, engineering wise, even within the grasp of a decent little hobbyist hacker..
I will say that this is not a product we're likely to see a ton of demand for, for a couple reasons…
it necessitates that you always have phantom available, so if there's no PA or phantom isn't available, you have to have your own phantom module, or a preamp that provides phantom… not only does that kind of remove the convenience generally, but having to include a preamp largely removes most of the appeal of an onboard preamp..
The other workaround is having an alternative power supply like an onboard battery just as a back up… Which again is going to remove much of the convenience, or at least make it kind of silly and redundant..
so I think if you see this, it will be a bespoke labor of love from somebody, convinced that this is the interface, they need.
ask somebody who has built some elaborate things to solve an imaginary problem for many years, this one doesn't even make my list.
I do kind of like the idea of something like Anthony Jackson's setup- if I remember correctly, his pick up is wired directly to an XLR with no knobs on board, with his preference to be for the pick up to connect directly to a transformer (paraphrasing, but I believe he says that specifically.)
in that specific case, I would argue it may indeed make more sense to have some sort of hi-fi preamp onboard as close as possible to the pick ups, and for somebody who has committed to the XLR life, certainly having phantom power this reinvented hifi active bass is a no-brainer.
Have you seen some of the bases overseas with chargeable batteries and a USB-c port to charge them?