Another risk is that your generator will fluently travel between the predetermined topics A, B, C, D, E, you create a lot of text, on the specified topic, but… it will somehow lack the conclusion? It will be just “a stream of text that ended at some point” rather than “a stream of text that culminated in a punchline”.
There’s a known divide among two styles of writing fiction, one of which is to plan the plot out in advance, and the other is to just start writing and see where it gets you. The latter method may produce events that feel more organic, but has a known failure mode where the author may realize that the story they’ve written ended up having no clear ending and then they have to throw away the last hundred pages of text and try to take the plot in a different direction from an earlier point. (Or in the case of writers such as G.R.R. Martin, have the whole project just sputter out after the plot has just gotten bigger and bigger with no satisfying end in sight.)
There’s a known divide among two styles of writing fiction, one of which is to plan the plot out in advance, and the other is to just start writing and see where it gets you. The latter method may produce events that feel more organic, but has a known failure mode where the author may realize that the story they’ve written ended up having no clear ending and then they have to throw away the last hundred pages of text and try to take the plot in a different direction from an earlier point. (Or in the case of writers such as G.R.R. Martin, have the whole project just sputter out after the plot has just gotten bigger and bigger with no satisfying end in sight.)