This seems more like a gameplay change then a map change. In other words I don't think it is possible to change the travel speed in a specefic map. You might be able to do it through planetary bonusses or abilities, though that would require that the planets used in the map are some new ones. So it might be possible to do, but will be somewhat complicated.

Depending on the layout of the map you could also just move the planets closer to eachother, though you propably aalready thought of this.

The in-game customizable random maps have always created very large phase lane length. I remember one of my first games in Sins I used it to make a multi-star map and it took near 30 minutes from go from star to star.

I would recommend downloading the galaxy forge program. It gives you much greater ability to customize maps then the in-game editor.

I have tried GF but it confuses me lol