House rules for epic antimagic?

[historian]

I apologize if this has been posted previously, but I have several questions relating to the functioning of antimagic particularly in the epic gaming context.

The pertinent parts of the rule are as follow:

The space within this barrier is impervious to most magical effects, including spells, spell-like abilities, and supernatural abilities.

Dispel magic does not remove the field, though Mage's Disjunction might.

Artifacts and deities are unaffected by mortal magic such as this.

Taking the rule on its face, it is impossible to dispel an antimagic spell, but would it be impossible to dispel an antimagic ability that was supernatural in nature (given that it is possible to dispel supernatural effects that have a duration longer than instantaneous)?

What if an immortal casts antimagic field? Would it affect an artifact?

Would the magic of a Deity function within the antimagic field of an Iron Colossus?

I know that epic magic is entitled to a dispel check (maximum +20 caster level) when cast inside an antimagic field, but this would mean that it would only have a chance of working when the caster of the antimagic field was level 29 or below. Would a similar check be allowable if the antimagic field were supernatural in nature?

Thanks in advance, it all seems a bit unbalancing.