I have had extreme success with this army.

SH Porfiria Navas Thunderbolt
SH Towed Field Arty
SH J-37 Ordnance Transport
X 3 SH Cavalier BA
SH Purifier BA
Merc Arbelest

Exactly 450 points. I lay down water, and use the transport for either 3 infantry pieces, or the arty, depending on wether my opponent has arty of his own. Thunderbolt can be quite resiliant, and the Arbelest is a nice supporter. Best of all, it is faction pure.

I know some of this army is going to be retired, but oh well.

I like Navas too, and boy are we going to take a hit when Liao Incursion gets retired. But LI ain't retired yet, so here's a similar (and non-retired) build like yours-

SH Porfiria Navas 202
SH Sniper Arty 61
Merc Zahn 30
SH Sylph 28
SH Elemental BA 16
SH x6 Minigun Cycles 48
SH Carmen Hern 63
448

With this one you can dedicate the Zahn to give the Sniper a more active role, either as arty or as a 2 Armor Piercing, direct fire tank drop. Use the Minis as chargemonkey screen or basing force, the Elemental as a capture threat, and the Sylph as your long reach fast baser. Navas is still Navas. :p And while Carmen isn't quite the Merc Arbalest, at least she doesn't explode if she gets heated up, and can better fend off infantry with her no minimum 3 ArP ballistic and 1 break-away, so use Hern like the Arbalest as the support piece. And it's still faction pure, and all will be active for a few months anyway.

I think you should tade out the Arbelast and put in something different. Like another artillary. I usually play 600 anyway.

Stahlie- your army is nice, but a single Elemental alone isn't much of a capture threat. I'd drop the minigun cycles for three Elementals or two Elementals and a pair of ATV's. Of course this is because of my personal prefrences and the pieces I have. Also I thought that Hern started with 4 damage ArmP, but I'm not look at her and haven't played her in a while either.

Personally, I'd replace the Zahn with our J-37 if you're playing in unrestricted, simply because carmen is fairly repairable. Don't forget that she's not a bad tankdrop either!