There's not much difference in brood area between a 14x12 and a 16x10 ("commercial").
14x12 uses long lugs, 16x10 uses short lugs.
Personally, I don't find the 'squarer' shape of the frame to be an "abomination", and I do prefer the longer lugs.
14x12 can be obtained in poly. 16x10 can't.
Changing from National to 14x12 can be done progressively, whereas 16x10 requires a Bailey or shook swarm.
For "stock control" simplification, I rather like having frame part commonality. Running 14x12 brood and SN5 in the supers, only the sidebars are different between the frames. Simples! And even my Manleys use the same topbar ...
Take the points and prejudices from this discussion, but DO make sure that you get your hands onto real hives running a different frame format *BEFORE* you invest time (and money) changing to a new format.
Try before you buy!
The simplest, most rational way of expanding brood space is to go double brood. I don't like multi-brood, but I can see why others do.
Its also probably the cheapest, smallest change to your operation and yet gives the biggest increase in brood space.
Brood and a half gives the problems of multi-brood without the simple flexibility of double brood. Disadvantages without the advantages, IMHO.