Neph - You worry far too much about tryin to be immune to everything.
Relax and worry more about having FUN. That's how you create a good epic character. Don't think about all the thousand different ways you could Win or Loose with a single action, it's counterproductive to good storytelling, which is what Epic Campaigns are all about - An Epic Story.
RangerJohn - If you want a Fighter-mage, my suggestions would be to include any/all of the following:
Fighter. Sorc. Monk(you likely won't be wearing armour, and monk is awesome. Every Adventurer should have the ability to punch someone in the face without provoking an AoO). Eldritch Knight.
And from Complete Mage, my favourite Fighter-Mage class: Abjurant Champion.
And now for some quotes
But you can easily fix your Banishability with those manacles that inflict Dimensional Anchor on whoever wears them. Just put them on, and cut the chain. Now you have stylish wristbands that keep you firmly in this plane.
While I disagree that it's required, there are two things I wanted to say.
Mechanically, cutting the chain would destroy them b/c it's part of the magical Item.
Thematically, I doubt most DM's would have a problem with doing so and just calling them 'bracers'
I'm not planning on it; more a case of, I'm going to have these feats for story reasons, what might I use them for?
I Personally disagree with taking feats ONLY for backstory purposes. 99% of the time the same function and fluff can be gained simply with good storytelling. Especially in a setting like this where the whole "Dead for thousands of years" thing is a VERY good way of explaining why you USED to be an epic leader of men but don't have any followers with you know... They've all been dead for millenia.
A:
I had thought that there were class restrictions on Followers, but I cannot see anything to that effect in either the DMG or the SRD. If you can find me a source please do
*Paraphrased from the ELH*
Optional rule: Exceptional followers
Normally You can only attract members of the Warrior, Expert, or Commoner classes. Using this optional rule, Adept or Aristocrats count as followers two levels higher, any follwer with even a single level in a PC class counts as THREE levels higher, and a follower with any levels in a prestige class counts as FIVE levels higher.
/snip
It's under the Epic Leadership Section, and apparently I was underquoting originally. Your tenth lvl followers could be 7th lvl PC classes or 5th level with a PRC(If you could find any for which they meet the Requirements by then)
Mind you, DMG also seems to explicitly state that you can have more than one cohort and I thought one was the limit.
The references to Multiples are there so you can REPLACE a cohort who has died or otherwise left your services. I don't think you'll find many who read it as saying you can have any number of cohorts (And if they do, they're wrong.

)
C:
While I am not going to push Diplomacy, he will have mex ranks in it, Skill Focus and high CHA. So the DC to convert someone from HELPFUL to FANATIC should be achievable
Not. Even. Saying. It.
What I am after is:
1) Is it going to better to take another 2 levels of Fighter to get Wpn Spec and an extra iterative attack
If you're going to be making attacks, Extra BAB is always useful, though as Shayuri pointed out, Weapon Spec isn't all that impressive.. Although it's still a USEFUL feat, and becomes more useful the more attacks you can make in a round.
PrCs are out as they would all stop his Aura progression, and while could ask to adapt a Bard or Cleric PrC I don't want to creat a hassle
Don't know much about the auras but why would a PrC stop his progression if a base class such as Fighter wouldn't? Do Auras specifically state that they progress with all base classes but not PrC's?