[SomeStupidPoint]

1. The strength of a currency is its ability to be exchanged, so forcing them onto several (possibly themselves compromised) networks increases transaction costs and changes the economics significantly. Similarly, hardened networks likely impose additional overhead. Finally, smaller networks are easier to perform 51% attacks on. If you can break it in to 10 networks, you only need 1/10th the power to 51% them each in turn.

2. My point was about the strength of the bitcoin network as it stands. And I think you agree that it's both vulnerable and non-trivial to fix, so Im not actually sure what your point is.