If you create a map with the galaxy forge, you can give everyone that is not in your spot (player 0) an ungodly high amount of starting resources via the edit > Players... menu. Just select the other players, change their starting values, and save the map.
As for working with existing maps, you can edit them and set up the same as above with either the forge or a text editing program (scroll to the bottom of the file and edit the values manually for all of the players except 0), or you just have to either play at a higher difficulty level so they get an eco boost, or continue to use the method you already use.
An alternative would be to use the dev.exe options differently. Instead of just setting up quick play (which gives them all of their research too I believe), from the root menu, press A to bring up the Change Galaxy menu. Then press D to bring up the change player menu, then hold down either G or H for some decent amount of time, let's just say 45 seconds to a minute each. That should give them enough to make it seem they have an unlimited amount once they get their economy up and running.