Nice idea however I doubt it would be used because in most scenarios you would just make gunships.
I'm not sure what you mean... the Specter gunship has 65 dps and price is similar to Mercy. It will take a Specter 35 seconds to deal as much damage as a Mercy (2300 damage) deals if it gets to the target. That is a lot of time for your opponent to prevent the damage being dealt.
Also, you generally try to preserve your gunships with air escorte, and fight from air cover.
Mercies after this change you would often want to use with a multi-prong surprise attack. You only need to get to the target, you'll need like 1 second for it to fire? And no return trip needed.
They will also deal slightly ok with T2 and T3 tanks and bots, 1200 mass worth of Mercies for 1 brick worth 1280 mass. 1 Mercy for most T2 tanks worth 200 mass. You only need a second for such an engagement. Very different from gunships again? They compare better to T2 bombers, but Aeon doesn't have those.