The Unioners were one of the first factions to establish a base in Koeln, system which is located next to their home bases in Duesseldorf. Now, as the Rheinland companies show interest in this system as well, the Unioners are going to leave them alone… until the regular trade routes are established.
Piracy in the Independent Worlds between Rheinland and Liberty, which were the center for Unioner former activities, are now a battlefield between two large armies. Trading in those systems had reduced to insignificant values, and the Unioners have to seek other areas where piracy is not that risky. Those areas may include Omega-5 and other systems of Rheinland.
Unioners in O5 indeed make, as already pointed out, no sense at all. Possible would be maybe Omega 7, but that is really pushing it, at Unioners have little influence in Western Rheinland.
Sigma 13 and maybe 19 would be viable options to expand to, as they are both close to the Unioners bases/ areas of operation.
Personally I'd prefer them to focus on central Rheinland though, and taking control (or trying) of most of the local black markets, as the Hessians are too busy with fighting their war on two fronts.
The LWBs story is a bit of a lackluster, more of the 'Hessian lackeys without a real purpose other than being bossed around', no own initiatives and nothing to make the faction more appealing overall (the Unioners at least get new ships). But that was to be expected, I guess.