To utilize either secondary function control (action release and safety button) on a 500 with an AR/AK style stock, you roll your hand from "fire ready" position up on to the stock/receiver joint. this is easiest done by dropping the gun to hip shooting position...
This kills the ergonomic reasons for a mossberg.
To me, a "tactical" stock is a traditional style. The definition of "tactic/tactical" is PLANNING an effective efficient armed resistance. Mitigating the positive attributes of a weapon design to use an aftermarket device that looks or seems cool or better is not in the "tactical" best interest of the user... but that is just the opinion of a back woods redneck feller.
Brent