I was thinking , what if when you enter a Raid instance there were vendors on the inside of the portal who sold you 1 time use set items a few ilevels bellow the set you get in the instance and which vanish the second you exit the dungeon.
Players wanting to raid with their guild but who do not have the gear for it would be able to pay some gold at the door and rent a full set or just a few bits of a set to allow them to take part and contribute, this would allow them to gather their higher T set without having to go through dungeons and raids that few people are doing anymore.
This mechanic could be applied to battle grounds as well and those total noobs at PVP could join a battle ground and rent a set for the duration allowing them to not only take part but contribute rather than being nothing more than cannon fodder that they normally are when entering with no pvp gear.
just a thought.