What's this? Make Gunboats and Gunships useful? HERESY!
But no, in all honesty, this is a solid idea, and should be looked at in more depth. No offense Lyth, but as you said, you aren't the best person to look at it stat wise, but the idea itself is sound. Maybe, if this gets implemented, we might see some reason to actually use more than like, four of the current gunboats.
One of the big problems is that people keep assuming something designed to fight smaller things needs to be smaller than the one designed to fight bigger things. The truth is that just is not so. Smaller gunboats like the old bottlenose were great against capital ships because their small size was good for dodging heavy fire but the vulnerability made a SNAC hit very deadly to it.
Big gunboats like the Ahoudori and Bretonia gunboat are way too big and slow to effectively fight capital ships which easily hit them and rip them apart, but they were extremely effective against other gunboats and fighters because they were durable enough to take some damage and had great firepower and arcs to take out smaller craft with ease.
That is the truth, even though it's the opposite of what you expect.