Personally I do reposition throughout the day, but that is personal preference.

It is more and issue on how you do the connections between parts so everything can speak with everything else.

My commercial split has a master half that I could use standalone, the other half needs that master to function though. I imagine that also applies on a scale and then you run into problems on how to do the matrix without compromising nkey-rollover.

Have you ever had a split keyboard before? I use a readily available one and the split does take getting used too.

Why do you want the pads? I work with layers for things like numpad and other specific keys and that works fine. I do come from full sized ISO, so I get why numpad is attractive, it does kinda negate part of the benefits of the split though.