another idea for the borgs. better than the previous one I think.
The borg civic makes all food related improvement negative ... ie: all the only improvements that are interesting to make are the Hammer+commerce ones (oups...energie + ...)
ex : farms = +(-5F)
mine +(-1F)
...
or even make all terrain produce 0 Food .. (I don't think it is possible though..)
but the civic allows for borg types specialists:
two-three types, each borg specialist produce the same gpp (if it is possible): : "borg-wonderboy" gpps (in order not to have too many GP):
borg-commercant=+energy
borg-producer=+production
borg-grower=+food
each slots can be created by buidling : ex: borg-manufacture : + 1-2 borg-grower slots... (you have a builgding that allows to build the borg robots quicker) or some can be given through the civic : to have a free start of food production...etc.
so the slots allowing growers (ie more food, ie more pop) are made using production. then you can work food... then grow pop. then stagnant : you have to create the next building that allows more borg-grower slots.
... indirectly city growth happens due to production
+ so the outer terrain of civ under borg civics will be heavily transformed into mining camps (as the only usable improvements are production ones)

it will really look borg like... (even more if it is more interesting to improve land + make borg specialists than to work un-improved lands for food)
the issue is that you don't really build pop with production, just an approximation of the idea
+the main important borg-specialist : the borg-grower, produces food.... a bit unrealistic for a production oriented ethnic...
hope it helps...
and is not too late...
or gives some ideas..
EDIT: it may work even better if mines and such give more production and/or energy than the borg-specialists slots ... so the city has best to : allocate slots for food, work the terrain into production mines to have hammers...
(so maybe you don't really have to have three types of borg specialists)