There already is a slider, in the in-game map maker, at least.
Phase Lane Length seems to say how far away two planets can be and still be linked by lanes.
Crank it up, and the map becomes a web of interconnecting phase lanes.
Move it down, and you'll get planets connected to each other in straight, simple lines.
Interesting - didn't know this (never played around with it).
The next question would be "is there a hard limit to how many planets a planet can be connected to?" For instance, can every planet be connected to 99 others on a 100 planet map? How many connections is that anyway, 100 squared?
A follow-up question to that one would be whether there is a practical limit that a human's eyes could handle in looking at such a map?
A POSSIBLE "HACK" FOR THE DEVS:
This is assuming it is desirable that we be able to connect every planet to every other planet, but don't want the map obscenely cluttered with phase lanes. Now, the game engine already has the ability to make any unit phase jump to any planet, through the vasari phase gate structure. So, to make a completely "open" map, 1) put a vasari phase gate on every planet, 2) make that phase gate invisible, 3) make that phase gate "intangible" so that units can pass through it and never interact with it, 4) make every player be "vasari" when the game engine checks a unit to see if it is allowed to phase jump using that invisible, intangible vasari structure, and 5) make every player be the owner of that phase gate when the check is made.