I mean if some idiot wanted to try this
Actually, this idea isnt idiotic at all, rabbits mix much better in large groups. Adding to an already established colony may cause problems, but if all are introduced simultaneously they tend to be better. There are occasionally the rabbits that will simply refuse to play nice with others though, and obviously they would need to be separated.
The rule tends to be 10 square foot/rabbit with any breeding doe requiring twice that. However that is a minimum. There also needs to be consideration that there will be no vegetation left, and they will also burrow down into the soil, creating the problem, that even enclosed, they are likely to escape given time…
There are a lot of shelters that do this for temporary rabbit date days, and rabbits bred for fur or meat are sometimes reared this way, alongside the fact there is a rabbit island where a population of rabbits got wildly out of control. I also know a guy who keeps about 20 free range buns in his house, no real problems.
Although its totally idyllic sounding, it probably wouldnt last-there is a reason that rabbits are regarded as a pest species: they are very good at destroying the environment in which they exist