I would looooove if the collect() function could take an Azure SQL DB stored procedure with params. That would open PowerApps to some very powerful and flexible enterprise scenarios where all the business logic and heavy lifting could be done server-side by the DB.
We could limit it to the first resultset returned by the proc to simplify things. The cherry on the top would be to be able to update a record with a proc, but hey, one fight at a time. ^^