It's not playable because we can't do VTOL. The only reason it was playable in Assault Horizon and Infinity was because they planned and partially implemented something like VTOL, but it's not in any of the other games.
I’ve played a couple games where you could use vtol (lethal skies 2 and dropship), in a (fast paced) combat scenario its next to useless and an awesome way to get blown out of the sky. In Lethal skies, it was specifically used in a rescue op where you had to land into a prison to pick someone up (you could use vtol in a few other missions but they were few and far between and it wasn’t required). Dropship was basically kill a few guys, land to drop off some ground vehicles and take off again to kill more guys, so vtol was basically the premise of the whole game.
It would be cool if it could be used in a combat scenario where you’re being chased and had to immediately halt forward movement and let the enemy pass you, but that’s what the PSM is for I suppose.