The EoMR/ME rules look like they extend well to an epic spell system. Maybe it is not so surprising that their anti-magic rules might also work well at epic levels. If we are talking about a Supernatural effect (like a dragon's breath weapon), would it be the source's hit dice that is used as a caster level?
I also recall something about incorporeal creatures disappearing inside an antimagic cone/field. Or maybe it is an ethereal creature? Does that happen in EoMR/ME too?
As for the SR; to absolutely match the core rules, an antimagic field would have to be a minimum of SR 40 to block all spells by non-epic casters. That's very high considering it could be generated by an 11th level caster. I wouldn't allow it to scale with CL. If I did, then I would make it SR 20 + caster level. CL capped at 20 for a maximum SR of 40.
If you want to make greater effects, use higher level spells. +10 SR/3 spell levels might work. If a 6th level spell gives SR 40, then a 9th level spell could give SR 50, a 12th level spell could give SR 60, and so on. If scaling with caster level is a good idea, each 3 levels would increase the cap on caster level by 10.
This idea is pretty rough, and maybe it should be in its own thread. I just hope that UK doesn't work through all the variations on this before publishing. It's been delayed enough.
I've been thinking about the other kinds of immunities; SKR's site made me think. I think that a paladin's immunity to fear needs to be more subtantial than +10 to saving throws vs fear. +10 + paladin level would be better. I think the other immunities could be handled the same way: +10 +1/class level, where the class is the one that provides the immunity.
For saves that give half damage, you could add a rule that if you save with a margin of 20 or more, you take no damage, just as if you had evasion or mettle.
If something doesn't allow a save, you get one anyway, but at a -20 penalty (this number might vary).
I like the notion that elemental immunities be based on hit dice. Resistance of 5/10/20 per hit dice, or something similar. My only concern is that a 1 hd creature that is immune to fire (but without a fire subtype or anything) would have less resitance than a 1 hd creature with fire resistance 10. Maybe there should be minimum values. Immunity can never be less than resistance 20 or something.
Anyways. While I have high hopes for the release of the various chapters of the Immortals Handbook, I don't think the material on immunities is anywhere close to being published.