A while back (http://cuebiddingatbridge.blogspot.com/2010/08/deep-thoughts.html), I suggested that he circumstance of a known two-fit scenario might best call for an "ask or answer" resolution of a ide "key card." I am more and more convinced that this makes sense.
The major time I would see a clear two-fit scenario would be a raised response in a minor converted to the major. For example, 1S-P-2D-P-3D-P-3S. This scenario reduces cuebidding space to unwind the strength of the diamond suit, as only one person will be able to cue (or not cue) diamonds. This lends itself somewhat to the "ask or answer" scheme.
The trick may be in deciding when a suit becomes sufficiently focal to call for an "ask or answer" scenario. Obviously, it seems that an agreed minor is and will be the focal side suit if a major is later agreed and if space was such that the minor could not be cuebid reliably as to internal controls. Also "obvious" seems to be that a competitive situation may call for the "focal suit" to be the opponents' suit, which would be a permutation of the idea for a different cause.
An example of the latter might be the following. You open One Spade, LHO overcalls Three Hearts, and partner bids Four Hearts as a strong spade raise. You want to explore slam. The classic method here is RKCB or cues. Perhaps a reasonable alternative is an ask-or-answer scenario. Ask with control in hearts; answer without.
Similarly, consider partner opening One Diamond, a 2H overcall, and you making a negative double. This is passed to partner, who splinters 4H. Passed to you. In that scenario, it might make sense to have an "ask-or-answer" scenario for an implied focal side suit -- diamonds. Perhaps Responder asks with the diamond King but answers without it.
Boy am I wanting better mga-rules here. I think there is something to this.
As I was just smoking a cigarette, another thought occurred to me. My wife is a newer player and thus afraid of RKCB still. When I try explaining it to her, the Queen ask always gets in the way. We all actually hate that part of RKCB anyway. The damned space it takes, and the question of whether 5H is a Queen ask after a 5D answer, hearts agreed. The 1430 or 3014 problem.
So, let's suppose, for the sake of argument, that the auction was one where Exclusion makes no sense (or where your partner does not get Exclusion as a concept -- my situation). One might make RKCB easier if the ask-or-answer sceanrio was used.
Bid 4NT with the trump Queen. Partner then answers a simple 5C = 0 or 3, 5D = 1 or 4, 5H = 2. No 5S response. This could even be easier. 5C = 0 or 4 key cards, 5D = 1, 5H = 2, 5S = 3. In other words, regular Blackwood, with the King also counted. The Queen problem is already solved.
Without the Queen, answer.
So far, easier, with no damned Queen-ask.
Advanced players, however, could keep the regular 0/3, 1/4, 2 structure. Then, the "void show" coul be cheaper, or a wrap-around structure used. In the latter, 5S+ could be bid with, say, 4. With three, bid 5C and 5D asks for specific Kings.
In other words, using an ask-or-answer structure to answer the Queen-ask problem could make for an easier THIRD version of RKCB (RKCB, 1430, and IQRKCB?). "Immediate Queen RKCB" or just "IQ" for short. Baby IQ would be the regular Blackwood-steps "RKCB." Advanced IQ could be an enhanced RKCB with wrap-arounds or cheaper King asks or whatever.