BBF is a great forum. The talent there is quickly obvious, and it is a great place to bounce ideas out there. One recent discussion convinced me of the merits of a new idea.
The concept is simple. We are all familiar with a 5♥ or 5♠ call as a "quantitative" raise of the major, asking about trump quality, whether we use it much or not. The diamond suit, however, does not allow us to make that call, because 5♦ is game.
However, what if 5♣, in a diamond-focused sequence, served the function of the "quantitative" raise? I mean, if the alternative is Exclusion, that's lousy, rare, and possibly meaningless anyway.
An example. You hold AK-AK-AK in clubs-heart-spades, with a stiff diamond. Add in a Queen for good measure. Partner opens 2♦, weak. What now? If partner an play diamonds for one loser, you can count 12 tricks. However, nothing will really allow you to find out exactly how good partner's diamond are.
So, you bid 2NT, which you play as Ogust. Fine. Partner shows a good suit but bad hand, the latter being obvious. But, what is a "good suit?" If partner needs two of the top three honors and three of the top five honors, he could have KQ10xxx, and that's not good enough. With the new tool, however, you can bid 5♣ to show slam interest, with a small stiff in diamonds. If partner has KQ10xxx, he signs off. With KQJxxx, he signs off. With KQJ10xx, or AQJ10xx, or AKJ10xx, however, he has an easy 6♦ call.
Suppose that your stiff is the Queen. If partner's response to Ogust is 3♣ (bad suit also), then he could still have what you need. Now, however, 5♣ should show a stiff honor (because you are not allowed to be an idiot, by agreement). If partner has something like AJ10xxx or KJ10xxx, he can probably play this for one loser, and he accordingly bids the slam.
This same approach would work after a 3♦ or 4♦ opening, as well as others.
I'm not sure that there is an easy solution for when the focus suit is clubs. But, the diamond solution is so friggin' easy and obvious. A 5♣ call is so obviously strange looking at the table that it would be hard to forget. I cannot imagine 2♦-P-2NT-P-3♣-P-5♣ not triggering partner's mind to think hard.