Why do you have to manually launch mixed rockets?
This mod allows you to send a signal to a rocket silo and the rocket will (probably) launch. The mod adds its own "launch rocket" signal, which is the default, but you can choose any signal. You can also choose the destination, or "Auto," which will automatically determine the destination based on the signal count. If the signal count is > 1, it will search for a platform with a matching number at the beginning of its name: e.g., sending a signal with a count of 6 to a silo in "Auto" mode will try to launch the rocket to "06 My Platform" or "6 Space Platform" or whatever. If no suitably numbered platform is found, the rocket will not launch. If the signal count is 1, it will try to route the rocket to a sensible location based on logistics requests, but I'm still working on this part. Rockets that get a negative signal will not launch, but you can change this in the options. An empty rocket or a rocket with a destination set to a platform that is not in orbit will also not launch. Rockets that are getting a launch signal but are blocked from launching will sit there with a "Zzz" icon like trains with nowhere to go.
You can't actually specify the destination of a rocket via Lua, so this mod uses a hack: it deletes the rocket you launched, and then spawns an invisible rocket silo on your space platform's surface and launches a second rocket from there, which is the one you actually see. Since that is just a bit janky, please don't use this on your favorite save without making a backup. Also, logistics requests won't be shown as "on the way" until the cargo pod is actually about to land, because the game has no way of knowing that the rocket is associated with that request. I don't think there is anything I can do about that.
If you like mods that help out with rocket logistics, you might also like Rocket Cargo Insertion, or if you'd rather not worry about rocket logistics, try Telogistics.