[RealDarko]

Yeah, that much i heard about it, that there was a consideration to mate a pre-existing airframe with a captured German jet engine. This is where eventually Yak-15 comes from.

But was there an actual Lavochkin attempt to mate a LaGG-3 airframe with a jet? And why a LaGG-3, why not some of its more modern derivatives - La-5 or La-7?

Was that initial idea ever considered any further than "it would be cool to stick a jet onto an existing airframe, but unfortunately we don't think it would work"?

I don't know what they used the Lagg-3 airframe, I supose that is the best airframe of the time of the trial, or at least the more tried. But yes, Lagg designed the Lagg-3RD with a jet engine and the strange nose we see in the game, they also planned to add the two cannons over the jet engine.
Anyway the plane was not accepted for production.
If I have time will scan the info I found in my book