Hmmm.
Some updates (no mesh changes yet though)
I'm going to redo the missile launchers. They do look funny, though I can't put my finger on it, so I'm going to redo them from scratch, starting with the shape of the original Ursa's missile launchers. Then skewing them forwards, softening the edges, and whatnot. While I'm at it I'm going to clean up those guns at the bottom... messy.
I'm going to make the triple barrels spin, but the gun hardpoints will
not spin. It's purely cosmetic.
How does the cockpit need work? I think it looks fine.
I think the engines look fine, too. They're actually what I consider the best part of the model.

The original Ursa's engines were skinny too.
The name Ursa Mark II is staying, because A) That's what the concept art is and B) It's clearly a sleeker evolution of the old slow chunky Ursa, in the same fashion as the Herc II. As such it will probably have Herc II/Artemis style sleek skins. But I can't paint at all so it's going to be someone else's job.
And it's been overused because people design 'Mark IIs' that bear no resemblance to the original. Scorpion II, Valkyrie II, etc. Not to belittle their fine work, but that shows a lack of imagination.
Venom: your interpretation is still too chunky for my tastes. I much prefer mine.

I'll work on this mesh and get back to you. I'm in FRED mode right now so it might not be until after the weekend, though.