A Maus in plastic would indoubtedly be nice, but I agree that it's unlikely to ever be a priority for Rubicon - there are two out there already (Blitzkrieg & Warlord) with two more incoming (Heer 46 & JTFM). A plastic kit would be cheaper (the existing ones are at the £50 mark & the two coming are likely to be similarly priced) & potentially better/more accurately detailed, but I struggle to put the one I already have into games (it's a lot of points in any system).
As Pinky said, it's not the most interesting thing to look at (I tend to think 'just about mobile outbuilding'), though that does mean your painting canvas is interestingly open.
Rich H's Ratte will probably turn out amazingly - his scratch builds are things of beauty & I suppose that you could have use it as a piece of gameable scenery in its own right - fighting compartment to compartment through it (& as JTFM are going to cast it we could all have a go if we so desired, though the price might be a little prohibitive).
Oh yes, I'd rather see the E series vehicles done than a Maus - though I admit it's about as likely.