So four models: P101, P103, P105, P107, two are "BTR". Each of those is split A/B and good/better/best.
As others have stated, A/B is obviously black and white, and good/better/best is likely 3 capacities.
I don't agree with any of the speculation on what the models are though. The "BTR" groups them into two pairs. This means 2 carriers + wifi doesn't make sense (what's the second wifi model?), and neither does 3 carriers + wifi (not two pairs).
Here's my bet:
wifi @ 8, 16, 32 GB
wifi + 3G @ 8, 16, 32 GB
retina + wifi @ 16, 32, 64 GB
retina + wifi + 4G @ 16, 32, 64 GB
The retina model may include other upgrades such as faster processor/graphics, or improved camera.
This covers the full range of the market from low-price for kids/educational to high-end for people wanting full features in a smaller form factor. I don't think this is an instance of over-complication so much as Apple compensating for not have a "last year's" model of the iPad mini for the low end.