If you're happy to pay whatever it costs to host then there's no other disadvantage to this.
The only thing I can think of is if you somehow end up at odds with an admin of a big instance and they defederate your instance. Or perhaps in the future major instances decide to only federate with instances of a certain size, for some as of now unpredictable reason
Which criminals though.
Wage thieves? Polluters? Tax evaders? Or just the poor ones?