I'm like 99% sure that xp to plat will get a massive thumbs down, but it deserves its day in court.
Also what about spending xp like a fame-point buy for a seperate list of no-drop consumable or clicky-with-charge items?
Possibly examples:
Something like the Tiny Statue of Ritual Burial or w/e for FD
Minor Illusion/Shapeshift
A reverse ressurection item that ports you to your last corpse without clearing xp debt
Food/drink with stat/save increases
Vah banners (this should spark some interest, good bad or other)...you'd be required to have the original banner/flag/whatever, but could summon a single charge (or whatever number of charges, hell make the charges stack) copy of a banner so you could carry useable versions of different banners without obliterating your bag space. (i.e. I'm wearing my final Vah back but I've got 2 charges of Sraen Banner in my ammo slot)
Ammo slot proc items with charges
Gate necks to odd places with charges
Speed of the Wind clickers with charges
No-rent special effect augs (like searfires/misc worn buffs)
No-rent worn illusions (like halloween masks)
No-rent pet gear
I'm harping mostly on charges b/c it IS a completionist game, etc etc, and eventually there is nothing left to obtain other than consumables.
Deity spec %
Also I don't know if it's possible or not, but while we're looking at spending xp, are we looking at giving toons something to do with all those unspent AAs they racked up and can't do anything with?
On the non-consumable end, I'd like to suggest type 8 aug alternatives (for those who don't have deity augs in/don't want to do their deity aug quest), an extra vah pole(!!!!!), charm credit (again, the xp-for-plat issue, but it's no-drop plat, and as a plat sink, let's face it, charms are the purpose for farming, it's a self-perpetuating plat cycle, not a sink)
EDIT: Also stylish pet summoners, or clickers to illusion your pet into something really cool like a little dragon or some other neat model.