>> Actually, this too confusing feature that allows changing prefix args
>> during the repeating sequence increases code complexity enormously.
>> For posterity I'll leave here the patch that completely supports it.
>> But this feature will be removed (unless someone will ask to leave it):
>>
>>   C-x } }  C-1 C-2 } }  C-3 C-4 } }
>>
>> Only this will remain:
>>
>>   C-x } }  C-1 C-2 C-x } }  C-3 C-4 C-x } }
>
> Well, it may be slightly on the confusing side, but it does feel
> natural, I think?  So I think fixing it is better than removing it.

I hesitate to make such massive change in repeat.el on the release branch.

I have more patches for repeat.el that I'm unsure about to push.
One of them is a patch that allows kbd syntax for 'repeat-exit-key':