Devyn,
It is never good to heap layer atop of layer when it comes to floor coverings. Your vinyl may be pristine but that isn't where the potential problems lie. Under that vinyl should be a layer of 1/4" plywood underlayment that was installed with the vinyl. That plywood is super problematic and contains voids and has voids under it that will wreck a rigid tile installation. Beside, why would you spend money for a tile installation that depends on an old vinyl installation to survive. It just isn't prudent.
Same goes for vinyl that is permanently and gloriously glued to a concrete substrate. Why would anyone spend money on a tile installation who's life depends on how long the vinyl will stay bonded to the concrete? Tile floors live longer when they can breathe a little. Trapped moisture under a vinyl covering wouldn't be good for a tile installation and all concrete contains moisture from time to time.

Vinyl flooring over time can shrink and draw and destroy a tile installation.