Heya! I’m a new user to the forum, but I heard this is the place to come if we have any Ideas on how we could improve the game, so here it is, my suggestion on a way that could improve Arty for a better experience indoors on maps such as most of Underground, or the last building in Bridge.
I suggest a theory to make the laser that the designator Arty already has shoot out a thinner, much less powerful version of Kira’s orbital strike, for a couple seconds at a time. Rather than just a targeting laser, an actual weapon as well.
It would work much the same way as Kira’s laser, the player would have to hold down the activation button, and aim with his/her mouse, but rather than coming out of the sky, just replacing the non-harmful laser used to target for the Artillery strike.
The laser will only be able to be usable if an artillery strike is primed for shooting, but while one is ready it should be able to damage over time for around 35~50 on a single Merc every half second adding up to a max of 140~200 health if it makes complete contact with an enemy in a perfect scenario, but an orbital strike will only be called when it would normally be able to, keeping the laser still. A sort of balancing so that the player couldn’t use the laser as a weapon for a long time, then call the Artillery would be the designator/weapon overheating if the laser runs too long, that being around 2 seconds. In comparison to Kira’s laser, hers lasts a good while longer, but the satellite is also in orbit being able to keep temperature down better.
An orbital strike being called will cancel the ability to continue using for the rest of the duration of the laser’s normal ‘free shooting’ time. Vice versa, using the laser as a weapon will eat up an Artillery shot (due to the people manning the cannon wondering what the heck you’re doing, and missing the battlezone completely 
). Every enemy it makes contact with gets an instant 10 health damage, so it’s up to you if you’d rather focus fire, move over your enemies constantly, or, of course, call in that orbital strike.
Essentially, a damage over time continuous beam laser that comes out of Arty’s designator, like the Focus rifle seen in this clip from Halo: Reach. https://www.youtube.com/watch?v=cbSDMNcQ6RU
Hope you enjoy my suggestion, thank you!