Currently, it's impossible to, say, specify multiple "fq" clauses when using Streaming Aggregation due to the fact that the c'tors take a Map of params.
Opening to discuss whether we should
1> deprecate the current c'tor
2> add a c'tor that takes a SolrParams object instead.
I don't see a clean way to go from a Map<String, String> to a (Modifiable)SolrParams, so existing code would need a significant change. I hacked together a PoC, just to see if I could make CloudSolrStream take a ModifiableSolrParams object instead and it passes tests, but it's so bad that I'm not going to even post it. There's got to be a better way to do this, but at least it's possible....