Took me a moment to figure out what you're asking about splicing together but it should pose no problems.

How do you plan to "light-up" the MG34? I can see you drilling it out to accept some optical fiber but hiding the LED seems a bit problematic. Now the LED can be mounted low in the tank and out of sight so it would seem necessary to drill out the pistol grip and feed the fiber in from there.

However, in the instance that you can find a proper tanker figure that can be posed to shoulder and fire the MG, then you could feed the fiber through a hole drilled straight through to the buttstock, on through to his shoulder, down his body and down through the cupola hatch.

Apologies for the excessive problem solving... Seems I'm overly concerned with scale issues.

-Harquebus