"Elemental resists are pretty easy, unless you're talking about Void. Can even do some materials choices to leave the rest open for enchantment."
"Resist All.. well, the easiest way to get that is to get armour that has an Elemental Armour spell as its enchantment, then do a plain suit. That's fairly tricky, but it'll free up an accessory slot if you use a ring, because they won't stack."
"If you do want them to stack, that's.. well, it's hard and tricky, but possible. It'd be best to pick all save element X, which is weak, and then you cover that with a gold-or-better Emblem.
And yeah, that's assuming you don't want Void Resistance too. That's probably too much."
"Outside of Death, there really isn't a status immunity thing. But you're high level adventurers and you probably have good saves. Get yourself a 20 or 30% bonus and it'll be just as good."
"Armour that interacts with weapons? Generally no, unless you're using alchemically-treated armour that has weapon effects on it. If you've got something specific in mind, though, let me know and maybe I'll take a crack at it."
"What do you want mana regen for? Doesn't it come back after fighting already? If you want it in-combat, it's better to have that sort of thing on a staff, not armour."
"Counter/Reflect..
Something to grant a skill or boost the power of a skill is workable. Do you have a skill in mind?"