Custom API with scripting
I know that'd be a whole new undertaking but why not dream a little.
What'd be awesome is a custom API capacity that'd allow us to write scripts/functions to return precalculated data on request.
Write a function that finds all deals with a certain title (as a parameter), sums up their values and returns the result. The client app only sends the title and gets back the sum.
Yes it's now (kind of) possible via normal API but doing this server side would be infinitely faster, cleaner client-side and great. And it would open a whole new world of possibilities.