I'm taking this from another angle here. Normally, balance designers / game directors / etc have a reason they don't grant a request for a feature/addition to a game. With all these posts regarding boosting XP in RK missions to the level of SL missions: I'd like to know the answer to why isn't this being done. Surly there is a reason. Here's some of what I was thinking could be possible explainations:
Money?: Right now FC forces you to do SL for XP if you want to go at any reasonable speed. SL means you're a paying subscriber, I get that, but you can't get to 220/x/x without a sub. You will still need to venture out into SL to do the 201-220 game. It would also put froobs in with subscribers which could get people to flip to a sub to continue the journey with the friends they made along the way.
Player Time Invested?: Hmmm, I wouldn't think so because as it stands now, if you want to level quickly, it's Kiting and that would stomp what we could get from RK missions even if they bumped them to SL levels of XP.
You'll miss out on the Nascene/Ely/Schoel/Ado stuff?: Again, I dont know... maybe, but people are generally doing that already, with the exception of Nascene - much of that ground is covered by a lower level character.
Again, this isn't me pleading to the devs to make this happen, but more of a "Why not?". If you think you know, by all means, enlighten me.