There is a concept in bridge where one partner auto-answers an assumed RKCB. The classic example might be that 4H Texas followed by a 5-level bid is Exclusion RKCB, while 2H Jacoby followed by a 5-level bid is esponder ANSWERING an "implied" 4NT RKCB from Opener (an idea I have heard to be attributed to Meckwell).
A while ago, I proposed a method whereby immediate answers in some contexts might be agreed as showing or denying a critical side suit Queen. In other words, imagine spades agreed, with clubs an obvious important suit. In this sort of scheme, the person bidding 4NT might have the club Queen; if not, he immediate-answers as if partner bid 4NT, denying the Queen.
Well, another possibility is in the context of a splinter bid (or other shortness bid), where there is some ambuiguity as to whether the shortness is stiff or void. In that situation, a plausible scheme would be for the person not knowing the answer to immediate-answer an assumed EXCLUSION 4NT if he lacks the Ace in the short suit -- a sort of Bluhmer RKCB Answer?
Consider a simple example (not that this would be the ideal place to use this -- it is merely an example). You open 1S, and partner blasts 4H, which you play as a stiff or void, support, and 13-14 or so HCP. Whatever. Opener could bid 4NT with the heart Ace or could bid, instead, 5C/5D/5H/5S as EXCLUSION RKCB answers, denying the heart Ace.
This would alleviate the need for showing the void, in a sense, which saves space, and would allow Responder with the void to know that partner has the Ace in the void suit if he asks (which might have some impact on Slam Last Train bids or something like that).
The same thing could be done in reverse. If you are the one who showed shortness, you could ask with the stiff but answer with the void. For example, after a 1S opening, you splinter 4D. Partner bids 4H as Last Train. If you accept with a stiff, bid 4NT. If you accept with a void, answer RKCB, promising the void.
This type of concept could be extended into other ideas, as well. Suppose, for example, that you know of a 5-3 major fit, but YOU also know of a 4-4 minor fit, partner being unaware of that second fit. Maybe 1S-2H, 3C-3S, cues, and then you are about to ask, having 3-5-1-4 shape. You could use 4NT ask straight RKCB but 5-bids as RKCB answers (maybe 6KCB answers?), establishing thereby clubs as an alternative fit!
This last concept is very promising. There are a lot of auctions where there is some ambiguity as to whether a call (like 6C in the example) is a choice call or a further inquiry. This type of structure would solve that problem.