Doesn't the festung support have relief inf, arty officer and mortar HT all together? That could be great for utilizing the arty officer plus you get to bring in relief troops by popping the ability at beginning of big skirmish.
Festung Support has the Mortar HT, Smoke Bombs, Relief Infantry, LeFH 18 and Sector Artillery. No Officer, unfortunately.
I, too, have been wondering about the use of the Artillery Officer to help myself in the Infantry War, especially since there's a Tiger Doctrine with it, but I'm not sure yet.
Hell, I'm even considering Ambush Camo.