As this information is apparently valuable to healers (since that's how they gain experience), I'd like to see an offhand item that allows a healer to "observe" a chosen fighter, causing the healer to intently observe that fighter and how they kill monsters. It could be a staff, charm, or coffee cup just as long as it serves the following function...
With a healer observing a fighter (in the same snell, of course), the game would treat that fighter as the healer's "pet". As with pets, anything the fighter tags, the healer would count as tagging as well (I'm hoping some serious code reusage from the pet code could happen here, but with CL's brittle code base, who knows... :\ ).
And as with pets, these proxy tags would not generate share experience, thus preventing any exploits.
It could have a rank cap on it, but I wouldn't at all mind if it didn't have a rank cap: It was fairly depressing to learn that a fighter who has more ranks than me gets ~3 ranks on a BP hunt while I'm lucky to get one (plus the exp gain from it would drop off at the appropriate time due to the naturally higher slaughter rate for healers). This massive gap in exp gain as a healer vs. that of a fighter means trying to catch up is futile, which in turn makes me want to play my healer less (and I KNOW I'm not alone in this regard).
With the ability to "observe" fighters, young healers could gain experience from playing like healers (instead of tagging or trying to tag) and would have a REAL means of progressing to community level instead of just baking in the library for a year or so.