1. those models have WAY WAY less then 3k polies
2. Mods don't have to be perfectly accurate(infact sometimes its in improvment when you aren't(example the Freeworlds mod for Freelancer had TIE fighters with shields but people still loved it.)
1/ That depends on the model you mean. Approx LOD0 (highest level of detail) for a fighter, bomber or similar small ship in FS2 was between 700 and 450 polys. The likes of the Hecate, Orion etc (destroyers, the largest frequently seen models) are about 2000-3000 polys, but this figure includes upwards of 15 individual turret models and
assorted debris. I don't have modelview installed at the moment to give a precise value, but I'm pretty certain of the approx amounts. (there were also some restrictions on said models; they'd be traingulated by default, and you weren't allowed open / intersecting faces)
2/ I realise that, no argument, what I mean is in terms of converting over existing assets it might be frustrating. I mean, who wants to reinvent the wheel?