I'm not sure where this is going, but how about:

"What clearance can you give me which will get me around to the east
of Potomac's airspace?"

Good enough.

...Or maybe he'll say, "Unfortunately, I can't get you anywhere near
there. The best I can do in that direction is blah, blah. Can you do
that?"

Well, he's at this point offering something. He could have been
offering something from the start, since he knows where I am and where
I'm heading. A more helpful original call would have been: "Potomac
can't take you right now. I can take you around twenty miles to the
East if you like, or to the northwest direct XXX. Which would you prefer?"

You seem to be expecting that he's going to say, "Bzzzt, wrong answer,
try again". It doesn't work like that.

No, it doesn't usually work like that. However, "you can't do that,
what are you going to do about it?" sure makes it seem like the
controller is playing that game.

"Say intentions" should
not be something pilots fear hearing.

It's not. But "we've revoked your clearance. Say intentions." is.

Jose
--
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for Email, make the obvious change in the address.