if you expand from the same system you expanded the first time, you'd get back into it again.
are you sure about the sytem you expanded from? most probably the system you jumped to had other criterias, why it was chosen (number of factions... influence level of factions...)? usually expansion in 2.1. takes range above anything.
bring it into retreat?
you'll win the most precious asset, 1 station, which will be the controlling station of system. normally the 1. largest starport 2. closest to entry point is the controlling station. there are notable exemptions from this, for exampel, when one station is orbiting an earth-like, it might be the controlling station, even if there is another station as big as and closer to entry point. e.g.: you can guesstimate (from what you wrote i'd guess one of the "large" station 46k ls is the controlling station), but you'll only know after the war.
for winning the other stations, you'll need to trigger more wars.
The system we wanted and was the next nearest location to us had six factions, we would have been the seventh.
Instead of getting that system we 'won' a system also with six minor factions, we are the seventh but this alternative brilliant, exciting new system (sarcasm mode) only has one platform 3,995 ls from the jump point and a main base at 4,021 ls. Not a system we are really interested in.
The one I had planned for only has one large, high tech station (to complement our location) PLUS.... This main station is just 752 ls from the jump point

Clearly the fair play Gods had it infamy, infamy I say, darned infamy. At the time of expansion it had six minor factions, the same number as the location we were allocated.
We are only a very, very small group of players and four to five systems is all we want and what we have, but I would much prefer having four to five system that are of benefit? (query)
Folks are saying any system is better than no system but I will tactfully not comment on that observation

and thanks to your much appreciated answers, it looks like if we did dump a system, we would probably just get it back UNLESS we change our controlling system location?? Engage thinking mode.
The so called 'retreat' mode is yet another feature I do not fully understand. I have seen minor factions remaining in systems untouched even though for weeks and in some locations, perhaps months they have had less than this 2% influence! Can this be because they are in their 'Home' location?
Being told we would get the largest station owned by a minor faction is confirming what I thought and in our other occupied system, this would mean we would have to have two elections for two main stations that are just over 4.6k ls from the jump point and only after taking those locations would we be able to take the useless platform that is just a spit and a throw from the jump point!! Did I suggest the developers have it infamy??

Am I being too fussy when I turn up my petite nose when we have the chance of taking stations that are over 4.6k ls from the jump point?
All good fun and rather than waste time trying to occupy systems I do not want, I think I will look for that invisible hunk of junk called polonium
Thanks again for the excellent advice
John