Oh, charming! I do crossover fanfiction, you know!

I put the Tenth Doctor into my League of Extraordinary Gentlemen. I also put Ten and Rose into the world of WarHammer 40K. I invovled Twelve in a crossover that included Mass Effect and ST:TNG.

Be it noted that in 2009 RTD spoke of his regret that a proposed Who/Enterprise crossover never happened. So it seems that , in principle at least, he's not opposed to crossovers!