So this mod has a great idea or so...
But artillery is so much range making rocket launcher a bit meh =/
Well if you mean by the weapon maybe could be nice but rocket launcher with so much range?? so my suggestion is making a tree tech range improvement? 20 tree tech and getting 2+ range per research till the 20 cap research to make it 44 range? how about that?
Progressive to your leveling ? just suggesting =p

Not a bad idea, though I really would start the rocket launcher with at least 30 range. Anything short of that is an insult to the user.

I considered adding a tech range improvement (which I could copy from the existing laser turret range research mod) but in the end I decided there's a very specific range at which the rocket launcher gets useful, and any higher than that gets stronger too fast. Eventually you won't see much need for the rocket launcher, especially in the late game when you use artillery. But with 44 range it has use throughout the mid-game as one of several ways you can demolish several spawners quickly. Basic rockets will destroy a spawner in two hits easily, and with enough damage research the explosive rockets can destroy 3 or 4 spawners in one hit.

If you don't see a use for this weapon in the mid game, here's a good technique to try: park your tank by a mass of spawners, just a bit out of aggro range. Put down a few turrets, and have some cluster grenades in your backpack. Now fire a few rockets into the nest, and when the biters come at you, let the turrets mow them down, and use that distraction to drive your tank up close to the nest where you lay down several cluster grenades, then drive back to the safety of your turrets. Rinse and repeat. Using this method, you can down a large number of spawners in one relatively safe attack run.

Artillery is stupidly strong!
And laser turrets is no doubt strong too but i never really used Rocket launcher... seems to me no good use ...
With Helicopter mod i use the rocket launcher so there i see good use =P
The thing is... in reality rockets has no good aim and range .. RPG which is what the main character uses ...
so having that "low range" is in compensate to low accuracy... if you increase rocket launcher range like .. a LOT it makes the rocket launcher better than a sniper xD
No offense or so intended just liked your concept but i would prefer a tech tree research so i could progress it early in game till mid game or so than start a game and focus fast on a rocket launcher instead of a grenades or submachines etc etc... just saying really .. also land mines is strong too xD

Well I'm too lazy to make the mod, but here's a similar mod you could copy code from if you wanted to make it: https://mods.factorio.com/mod/LaserTurretRangeUpgrade

You'll need to adapt the laser turret from the turret category to your rocket launcher which is weapon category.

Huh. Amusingly enough, I made this exact same mod a while back, except it had a range of 45.
And for exactly the same reason.

This was before Rocket damage was buffed naturally. Which I mostly undid because reasons.