I feel like a siege wouldn't be gameplay fun for anybody involved.
If LN succeed in the Siege, it means less Harmony supply ships to hunt, less Harmony online to defend the base, less UN to back them up, etc. How does that benefit LN? Equally it takes out a supply point for UN, who love having reasons to smuggle (there arn't a huge number, although the situation is getting better).
It's currently an activity source that doesn't block trade or interfere with any other faction. Besides, peaceful house border worlds are dead house borderworlds. You have an emergent source of logging here. Besieging it down might feel good for a few days, but then you'll have less to log for afterwards.
Just my 2 cents. LN should incentivise unlawful basebuilding projects as they create raidspots. I am biased, of course, but I've played lawful before and it's really fun when there's set places where you know you can get activity. Like KNF in Chukgoku back in the day, or outside Ainu depot.
THE SYNDIC LEAGUES
(A co-operative of Rheinland's outlawed trade unions, determined to take the underworld for themselves.)