First let me say this is excellent work you should do the rest of the Macross fighters.
Too hear that you got a VF-1, abet in a simulation, to handle better than a F-16 is most excellent. Now how does it compare to a F-22, it's funny they both have about the same thrust output. The VF-1 is much lighter though with a much higher top speed just by the virtue of the fact the F-22's intakes can't feed the engines much past mach 1.8+(some one correct me) as i read. But I find it interesting that Shijo pegged the output of an early 21st century fighter, and she more or less resembles the pre-stealth concept for the YF-23 Blackwidow II with the addition of the swing wings.
Regarding the VF-1's speed being limited by composition of materials, I wouldn't think so much as they are quite capable of entry into an earth type atmosphere from high earth orbit. I think the limiting factor for the VF-1 is aerodynamics, the intake shape, and onboard reaction mass tankage.
I know the fore fans are just superconducting fans for regulation of air flow and possibly feeding of reaction mass. Unless when the doors are closed the whole front half of the main engine and the fore fan are shutdown/disused. Leaving only the reaction chamber(a small torus in the engine), a reaction mass/coolant(most likely one in the same) injector, and the turbine linked to a superconducting generator. There is a diagram of the FF2001 in the Macross design works book, My scanner is dead otherwise I'd share, anybody else have that diagram?
But I digress,... the point is that once a VF-1 goes past mach 2.x(someone correct me on the most likely speed the intake on a VF-1 could feed up to), she's a rocket with 150 seconds at max delta V(Macross compendium). So first we have to ask, at what altitude would the air get to thin for the engine to sufficiently compress to use a reaction mass, then what is the maximum speed the fighter can be going whilst doing that. From there it's 150 seconds at max burn with maybe a bit of climb, wait till burn out and presto you have your answer.