Shadows and shaders would be the very last thing i would ever ask for. DBPro or not.
Using matrices is a big mistake for anyone after the first steps into getting familiar with DBPro. I dropped it after a few hours, and jumped into my own ground builder with Memblocks. I kinda left it around this years March to work on an easier shoot'em project, but this is what i managed to do in two weeks, so you should give it a go... It also real time casts shadows on itself without shaders or any kind of plus processing power!
http://trisplay.atw.hu/myeditor.jpg
The best thing is that what i realized since then, that you don't need to understand the horrible topic of Memblock, you just simply create a plain in a 3d editor program, and you can adjust the vertex data with... the vertexdata commands, very easily. You would even gain the advantage of having 4 vertex polygons instead of Memblock's 2x3 vertex triangle polygons.
But i didn't really mean the ground - however now you mentioned that would require updating yeah as well -, but anything else. Though those stereotipically looking terrorist guys look alright. Not by todays standards at all, but i like those.
Give everything its own burnt-into-texture lightmapping. Use a bit more polygon details. My laptop is a crap, still your game ran. So it basically means it will be fine with many many people. But this look right now is funny with these kinda spec requirements.
I just want you to see that i think if there is such an advanced game on the inside, it should look like that on the outside as well, so it does get recognition by the masses, and not just a couple hardcore indie guys here and there.
I would suggest that you released a gameplay video so you can interest some artist who you could team up with to finish this up in a pro form.
-In.Dev.X: A unique heavy story based shoot'em ~35%
-CoreFleet: An underground commander unit based RTS ~15%
-TailsVSEggman: An Sonic themed RTS under development for idea presentation to Sega ~15%