@Tag,
Have you not seen MMS before? everything here is a duplicate of that, other than the Holofield rules. (which likely will just end up being as MMS 1.9)
I was against MMS before, but the argument for making them this way is sound. They are a very glass cannon feel, their weaponry is rather powerful, but they don't have too much for survival.
They are a hell of a lot more survivable with the shields and crits on only 5+ and they still have some help from HF. So I think that they should have comparable durability to Chaos. And quite a few people have been using these rules for years without falling apart.
@Horizon,
All right on the re-roll thing, but how about lance-type weapons receive a -1 to hit if firing over 15cm, -2 if over 30. It would give your range-dependant defense thing, and would provide an added benefit against lances which cause multiple hits.
I also like the idea of lances being worse than WBs against Eldar, which this kind of does.
As far as Nova Cannon hits, they roll 2D6 and choose the lowest die for damage caused?