Give us a mechanism to link classic, retail achievements 2 way. It is annoying to farm all the stuff that i have already farmed back in the day during mist again in classic wow, also it would be nice to finaly be able to obtain the challenge mode dungeons gold rated xmog/mount and send them back to retail.
A way to accumulate all the achievement/mounts/toys/pets/reputations and sync them into 1 character in retail from classic and like wise a way to sync all the retail stuff back to classic al be it maybe expansion locked, for example the player gets all the stuff in classic up to the current expansion or expansion -1 (for example if we are in mop, we get everything up to cata that we have achieved and done from retail).
Would not mind it being a shop service or something that is added to the classic expansions release package, to prevent mass use/ddos.