Only skimmed this, but as an aside, I think we should not index BI to inflation. A basic income higher than the economy can support seems likely to lead to inflation, and if that's the case then the real value of it will fall to something we can support, which seems a worthwhile safety valve.
An interesting proposal, certainly. Have you carefully thought through the ramifications? (I've not yet, and I'm not hinting at anything, I'm just looking for more thoughts in the space).
I don't have a specific proposal. It would seem less likely to have some sort of "spiral out of control" type risk, though, since we've already got a BI of zero.
I should amend my previous statement, though - BI should track targeted inflation, it should not track actual inflation.