Has anyone built a custom solution for joining multiple searches with custom defined columns? It could be a pretty powerful tool. I imagine it to have a custom record with at least 3 fields - Left Table, Right Table, Join field, (and perhaps a Join type like SQL joins Left, Right or inner). Then, I would want to create a suitelet that takes the data from 2 tables (which are themselves saved searches) - perform the join in Suitelet, create an object, and throw it back out in a CSV file...

I've had a look at the documentation for the new REST based SuiteTalk API and want to try creating a GraphQL wrapper around it. Then it would be pretty simple to do something like that. I'm still waiting for them to enable the feature in my account to actually play with it.

doesn't the N/query module do this? Or are you wanting ad-hoc joins (which I want too!)

It does but I am talking about taking it to the next level

I am looking to do ad-hoc joins and michoel's idea seems even better. Although I suspect that hosting something like that could potentially require some serious resources (assuming Netsuite will host it for all users).

Prolecto has a solution for this called CRE (Content Rendering Engine) for all sorts of output options using templates (FreeMarker or TrimPath)