So after placing my original post in the wrong forum and getting some very useful feedback from the helpful people here (although I'm sure I frustrated some to no end), I've posted a second version (after a bit of wordy investigations) of what I'm likely to use for shields/shield block. I haven't playtested this yet, but it's more of a simplification vice major change that allows scaling. the potential rune towards the end is a bigger change and could cause problems, but if it works, would make the various shield block feats more attractive as options (outside Reflexive Shield). I think.