On the subject of trade ships, I've been attempting an interesting new strategy based around stopping the mini-freighter units from moving. My first plan was to gift a slowdown base to a minor race, and then declare war on them. It didn't work - they kept moving. But my next idea worked:
What you do is build a bunch of freighters, and send them all from one of your planets to an alien world. Practically any world will do. When the mini-freighters are on their way back (so the income per turn is high), you build 8 constructors, put them in a circle around the mini-freighters, build 8 starbases, and then gift them all to an alien race, preferably one who isn't going to get his starbases attacked if they're in that location.
The mini-freighters are surrounded, and unable to move in any direction, so they just stay there. You can then build a load of trade bases in the same sector - a good way to do it might be in a big ring around the 8 gifted starbases to stop them being attacked. You get the benefits of trade bonuses every turn, multiplied by a high base amount from being late in the route, and no need to build speedup bases.
(This seems to work in theory, but to be honest, I can't really be bothered to build trade bases; usually by the time I'm ready to build lots of constructors my cultural influence is flipping worlds all across the galaxy and I keep taking over the planets I'm trying to trade with. My main trade strategy is to swap techs for alien freighters and send them to the nearest high population system. Much less fuss.)
~SDC~