Terrahawks-wise, there were a fair amount of toys released in 1983 for a year or two. The figures and smaller ships released were a bit rubbish, wind up Battlehawk anyone? I like the 4 large vehicles (what you'd call DX versions) made out of plastic and diecast metal with minimalistic silver and orange paint scheme; these were, Treehawk, Terrahawk, Battlehawk and Hawkwing. The box art teases a massive Spacehawk, but this was never released, although there are pics of the prototype out there. They might not stand up to 2016 masterpiece scrutiny, but I always had a soft spot for them and I liked the way they didn't cop out with a completely out of place colour scheme, Takatoku X Bombers, I'm looking at you.
Yeah, must say, I agree with you about TB 2086. Beyond the great opening title sequence it wasn't much to write home about, but nice to see a bit of anime on the BBC at tea-time in 1986. Thought about the 3D printing option actually...if the digital 3D models are out there it wouldn't be to much of a problem to print them then modify them a bit so they could combine.
I am a bit of a blocky mech fan to be honest. There are a load of beautiful, fully posable, 'perfect' versions out there now, but I'm a sucker for late 70s early 80s Popy and Bandai.
I like parties, I like fun, I want to live in a hamburger bun!