I have a list a mile high of models I need but I'll settle for some massive high-poly space caverns. These aren't for sins, they're for the UDK, so go hogwild.

Awesome!

As for requests, I know one of the most popular ones has been for a new TEC heavy cruiser. One that doesn't look like a tank in space. 

For space caverns, I'm thinking a huge three-dimensional rock formation. Something that encompasses many star systems. However, since we're just using it for backdrop in movies, it wouldn't need to be a large network like that - just something that can be used in some of the scenes. I need several different versions, but I can probably cobble together the variants myself. Just need something to go off of...

http://ngm.nationalgeographic.com/2011/01/largest-cave/interactive/img/cave_4.jpg

I ended up remastering your seed ship for the DyiithJhinn Providence.

Getting base meshes that look proper tends to be, by far, the hardest part of making ships for me. Unfortunately, most your designs don't fit my world even with heavy modification. I think there might be 2-3 more ships I can heavily rework. Also, they seem to have a lot of ngons and normals and stuff I need to fix, perhaps due to conversion. Luckily, this is really easy and far outweighed by having a decent base mesh to work with.

Which is why I want to ask if you could throw together a few low-poly base meshes minus weapons and details for me some point in the near future.

Best regards.

If you're interested I could use some large freighter and gunboat-like ships that fit in with the Freelancer Houses (Liberty, Rheinland, Kusari and Bretonia) just to expand the ship lineup a bit for Sins of the Sirius Sector

Your question implies piracy, which I doubt is something Stardock and the forums support. I will say if you are a university student you may be able to access student versions on a trial basis from Autodesk through your university/college.

This sadly is correct.

Personally speaking I couldn't figure out how to use 3DS Max for hardpointing, Softimage isn't tough to use at all.

Pretty much this. I use 3DS Max for making the model, export as an obj file, import to Softimage and do my hardpoints, scaling, merging, etc.

What version of Softimage do you guys recommend 2011, 2012, 2013, 2014? 

I don't make models from scratch but I just use the XSI mod tool 7.5 for rigging and touchup. It's free and reportedly works best with the Sins converter.