Nowadays, full text search, multi keywords and facet filtering is just the implicit level of expectation of end users, because they use it every days in Google, shopping website, windows, etc... I think we should be able to offer this user experience in our Mendix apps.
In the market place, we have the global search module, which is based on lucene search engine (apache) . But it's a low priority side project and basic capabilities of lucene are still missing, like facet search. Worst, this module is not horizontally scalable, since the indexes of lucene are stored in the deployment folder of the app.
For horizontal scalability, We should offer connectors to external search engines like SOLR (from apache too ) or elastic search. These modules would implement rest api integration and include widgets or page snippets leveraging facet filtering with charts, etc.
In terms of deployment, the Mendix cloud should also offer the hosting of the search engine.