I'd say there are plenty of lawful systems that can be expanded into
...in the bubble.
Every lawful system in Colonia with four exceptions is under the control of an adopted faction already. Two of those exceptions are BGS locked, of the other two Einheriar was for a long time under Explorers' Nation control until they lost it in previous conflicts with pro-Anarchist groups, and Pennsylvania is under direct Council rule at the moment after the native Anarchist No Look Here Gang, having defeated the native PMF Consortium Pioneers, then lost the system again in the battle that marks the start of this Fifth Regional Conflict.
Or put another way, until the Reapers started poking things, every lawful system - which at the time, included Carcosa - was already subject to a prior claim as well. So, yes, to take Carcosa for the Nameless the Reapers have had to contest existing territorial claims. A hypothetical Loren's Accountants [1], taking Kojeara for the native Corporate Junkyard Dogs, would have had almost exactly the same issues.
In practice, the important precedents for Colonia are already set:
1) It's much easier to get an alliance to defend existing territory rather than to attack
2) You can try to take territory from an inactive group if you want but on your own head be it if they were just napping
3) Pennsylvania is cursed to be the doom of all who try to rule it
The interesting thing about this conflict, of course, is how it demonstrates all three.
The first one, of course, is arguably the question the whole conflict hinges on and why their respective answers to it are why various parties have taken the sides they have - who is
actually the defender here? Is it the Nameless, as the native faction to the system, or Explorers' Nation, as the first supported faction to successfully claim it?
(A related and also important question: does the same answer apply to the failed attempts, in the Third Regional Conflict, to take Desy from MCRN for the native Colonia Agricultural Cooperative? In terms of practical support for either side, the answer there was clearly in favour of MCRN - why this is the case is also a very important fact about this conflict, and perhaps also a lesson in the limitations of precedent: all situations can be unprecedented if you want them to be)
I think thats a reasonable timeframe to be honest in a real world real time game like ED but also something to be proud of, would it be the same if you had said 'It has taken 3 months'? Once the journey is over and the destination is reached I often need a new journey so a long journey is fine if I can do other things whilst on it. My main objection is that its usually too quick and simplistic and not realistic, like the WHN bases that popped up overnight one tick, Id prefer to see them being 'built' over a period of time or one this month and one next month so we can see progress rather than 'Ta da, now thats magic!'
WHN was particularly fast. Most of the Colonia bases, while appearing overnight, at least had a week or two between the relevant CG and the base appearing, so it could be handwaved a bit more as "they turned the transponders on today". On the other hand WHN did have three superpowers backing it from fairly nearby, and Colonia definitely did not.
(Some people made much the same complaint about the pace of appearance of the initial settlements outside Colonia, and felt that should have been slower and more dynamically linked to player activity ... which, yes, it
should have, but Frontier still don't have the BGS capabilities to make that work, and I prefer what we have to still sitting at a lone Jaques Station four years later)
[1] They're hypothetical, right?