I would say that the key point of interest in Spica is the three-way border between the Solomini, the Hive and the NA/PE zone, plus it's just about on the Imperium's radar. The fundamentals are excellent -- only Reavers' Deep and the Spinward Marches have the same potential for tension, intrigue and conflict.
Check out the GURPSiverse border, it's even better than the 1116 border.
Let's have lots of border tension, systems living under new masters, long range IISS "survey", client states, forward bases, rebel groups, spies, diplomats, trade opportunities, minor races, secret bases, undeclared border wars and skirmishes, pocket empires, state-sponsored privateering and refuges, deep space refuelling depots, unofficial technology exchanges, Imperial merchants, Imperial "merchants", and of course Fiendishly Cunning Hiver Plots.
Get all that sorted then fit the UWPs and allegiance codes to it, not vice versa. Traveller has always done this the wrong way around. You guys don't have to stick to the canonical (and crap) bottom-up approach for the usual reasons of setting/designer inertia.