Appreciate the reply! i have a few ideas for how it could be implemented without destroying the balance of the game.
For the damage i think the best option would be to significantly lower the AoE compared to the airstrikes you showed off, but still have one-shot damage for everything besides bosses. Basically a hellfire instead of the ALCMs.
In terms of ammunition i was thinking it would be a fixed amount per mission (Like how many missiles your supporting aircraft has in its loadout) but still keep a long cooldown cause the aircraft's line of sight got obscured or whatever. Like 20-40 something missiles per mission if you go with a AC-130 style aircraft that only has that ordinance. (Mind went to an AC130 cause i made a whole fictional aircraft design as a futuristic analogue, a helicopter or jet could also work most likely.)
Also a attribute of the designator that would help in balancing is that you need to constantly keep a line of sight lase until the missiles hit, so you would constantly be exposed to fire without a primary weapon.
I personally don't think it would be good as a secondary cause that would make it OP even with all these changes, but its also now in a position where its underpowered as a primary. I think a long range sensor of some kind on the other pod location to "Zoom" your viewdistance would be a good idea, so you could move your sight in the direction your mouse is pointed at and start designating targets. If this viewdistance was just out of the range of agro, it would allow for a stealth playstyle where you have to constantly skirt outside of their viewdistance to remain undetected but still capable of calling fire support on them.
This is what i mean by pod locations 
And a highly advanced illustration of the next generation multi system capable futureproofed high speed resilient architecture offgrid sensor suite developed for end users with demanding mission profiles and high operational tempo.