No, that's not ruining a good idea, that's just good business sense. How else do you market such a series unless you give it a set of parameters to conform to? The page count in particular adheres to the price point which would have to be solidified for each issue as to allow stores to buy the book.
The idea that it's 'laughable' to have a mainstream publisher publish a book by top creators with the mandate that one story at least must feature one of their characters? Hardly laughable. Why would DC publish this through their mainline output if it didn't feature their characters? The idea of Solo was top creators working on DC characters - If they weren't, why would the likes of Allred go to them in the first place?
And nudity restrictions are nothing - The book generally tried to appeal to a largely all-ages audience.
So it's not 'laughably' destroying a good idea, and I hardly find the restrictions 'harsh' as an artist myself - It's just business sense and having to work in a corporate environment.