Non-melee Spitfire Juggernaut is pretty fun! I'm not sure whether or not to take Hardened Platform 6b. So far I have taken it, and I rarely had to use melee for shield restoration, but when I did - that extra 50% was a lifesaver.
Before going the all 6 route for my Jug, I would skip final Siege Pulse evolution for at least 3 points in shields. And I always go Hardened Platform on him, especially now since I glitch him to get the shield to help counter that Hardened Platform dmg reduction penalty. Going 6a fitness also means you should really consider the bigger shield too, since you need more cover from being more fragile.
The shield is nice because it provides more freedom to be wherever you want to me. But if you can do fine without it, then don't worry about it.
For the Spitfire, always go for extended mag with either EB with Armour Ammo or HVB with Incindiary ammo. As this is the true Spitfire experience.
Jug already gets stability passives that I find enough if it works off host. And since I always go Adren Mods on him, I'd go Barrage Gear instead for more. But since your Spitfire is still only level 1, I can't understand you wanting the AR Gear instead.
On my new PS3 account I just unlocked a Spitfire 1 too, only too bad I don't have HVB yet...