Gravitic FTL

Is gravity instantaneous? No.

Might a gravity beam be complex enough to carry a signal describing every molecule in a human body? Doubt it.

How else might an sf author use gravity to rationalize FTL?

In Cities In Flight, James Blish cites the Locke Derivation of a Blackett equation which makes G equal the square of: 2 multiplied by angular momentum by C over a constant equal to about 0.25 by rotation. When this is tested in the Jovian gravity field, the practical effect is a field that abolishes the Lorentz-Fitzgerald relationship and is intolerant of matter outside its influence, thus an FTL drive, although we are also told that the formula predicted neither these effects nor their order of magnitude.

Blish, like Anderson, knew how to invent rationales for sf ideas.