The only crossover I can think of involving Nuku-nuku is one where Ranma and Pluto start playing increasingly bad pranks on each other, with Pluto setting Ranma up with the cat-brained android and the character from Boku no futaba no tsubasa. I'm sure someone can provide you with the link. It's The Best of Times by Ozallos.
Only one i can think of with A Ranma/Nuku cross, and Ryoga as a part of it is one where Akane beats Ryoga up after Ranma and Cologne train Akane And Nuku in the forests...
There's another where Shampoo becomes NukuNuku, although I can't find the link.
"So Igor wasn't kidding. Most people just ensure they won't die cold and alone by making friends...I gain superpowers and have mysterious voices tell me I did a good job. My life is a goddamn mess." -- Minato Arisato, My Life is a Goddamn Mess
Ah yes. Project NK Ranma. I really liked that one.
There's Rod M.'s Surreal World and Brian Randall's Process of Elimination. Both are multi crossovers where Nuku Nuku is one of the series that are crossed with Ranma.
I don't know of any Ranma/Nuku Nuku crossovers where Ryoga plays a major role.