I would suggest going more the ranged/helping route. Anything they can do that would be somewhat diverting to the enemy, somewhat distracting, and also hard for them to get smacked for it.
Ring of evasion is good (improved evasion somehow?), Definately something that grants a continuous flat chance of negating outside forces: ring of blinking (did it get nerfed? or am I just imagining things?), cloak of displacement, brooch of shielding, ioun stone to prevent the need to breathe (this would negate certain poisons yes?, or you could just give them a periapt of proof against poison), and a continual ability to see invis (and etheral if possible).
If they each have a horn of valhalla, blasting, fog, and a few others they can quickly make combat difficult for your enemies.
Mount him on something interesting (you have lots of money, make it something cool)
Just give them anything that grants an immunity or flat chance to negate, these abilities will still help them greatly. Make them immune to as many things as possible and give them items that do interesting/useful things.
Ring of evasion is good (improved evasion somehow?), Definately something that grants a continuous flat chance of negating outside forces: ring of blinking (did it get nerfed? or am I just imagining things?), cloak of displacement, brooch of shielding, ioun stone to prevent the need to breathe (this would negate certain poisons yes?, or you could just give them a periapt of proof against poison), and a continual ability to see invis (and etheral if possible).
If they each have a horn of valhalla, blasting, fog, and a few others they can quickly make combat difficult for your enemies.
Mount him on something interesting (you have lots of money, make it something cool)
Just give them anything that grants an immunity or flat chance to negate, these abilities will still help them greatly. Make them immune to as many things as possible and give them items that do interesting/useful things.