[gryn]

as long as you're willing to write a whole lots of data validation, constraint checking scripts by hand in the future, ETL scripts for non-trivial analytical queries (depending on what NoSQL you chose, but if you chose it for perf this one is usual a price you have to pay). and keep a very rigorous track of the conceptual model of your data somewhere else, or simply don't care about its consistency when different parts of your not-schema have contradicting data (at that point why are you even storing it?)

and that you ruled out using a JSON string column(s) as a dump for the uncertain parts, de-normalization and indexing, and the EAV schema as potential solutions to your problems.

the point is noting is free, and you have to be sure it's a price your willing to pay.

are you ready to give up joins ?, have your data be modeled after the exact queries your going to make ?, for you data to be duplicated across many places ? etc ...