Instant Vise Alignment

[Toolmaker51]

Creative system and approach, but a really common feature of milling vises are cuts underneath to mount fixture keys, many for jaws parallel or perpendicular to main axis of travel, the "X". That's what drill press vises lack.

That said, many find keys and fit to slot troublesome. Keys, being hardened, also raise concern about marring the table. Your idea curtails that too.
So, only real suggestion is milling the vise slots, (over filing) in accordance with stationary vise jaw.

For that, I'd clamp a good straight bar down, flip the vise, clamp securely to bar, and use DRO and/ or indicator to ascertain "Y" position.