Is moving payload masses during flight to restore mass centering, or to avoid having to trim, a useful approach? Note: Title was previously "Movable big missiles/bombs/tanks under fighter jets: conceivable?"

Example: lateral weight distribution in fighters

Fighter-bombers jets are small and lightweight in proportion to the under wings load (including payload but also external tanks) they carry which means most stuff can't be placed right below the body of plane and heavy payload (very big missiles and bombs) ends up relatively very far from the center of mass.

(Although some designs have a bay to hide payload, the bay is small compared to the maximum possible load of other fighter and they still have the option to carry under the wings.)

So here is a (possibly unworkable) idea:

Is it conceivable to mount heavy load on movable arms that can move weight left or right to adjust mass centering:


at under wing load installing time?
during fight?


The heavy load, including external tanks, would be automatically moved to preserve mass balance.

Example: longitudinal balance for cargo planes

The idea here is to move the fret of a cargo plane in the longitudinal axis, to adjust balance and minimize trim.
While I don't know of any airplanes that move load in flight for CG purposes, there are definitely airplanes that have various fuel tanks that can be used to trim the airplane during flight. Some of these systems will move the CG aft after takeoff for better performance in cruise, and then move the CG forward before landing for a more stable approach and landing.