I'm close and to make a serious point I've not been able to get excited about EP for the best part of a year because there's nothing for me to spend it on that'll make any difference to my game.
There is scope for 'super' extensions I think, extensions with multipliers of 12, 15, 18 and where the >lvl5 multiplier kicks in at level 1.
Some things I think would make appropriate 'super' extensions:
NEXUS bonuses.
Signal detection/masking
Accumulator
Protoyping
Factory lines
Material efficiency
In fact, given the way the points formula works all production based extension would be good for those without access to gamma facilities but a bit pointless for those with.