This is going to sound really stupid, but I have read through the rules pretty thoroughly, and do not see this information anywhere:
What constitutes a "Front Line" unit?
I realize I have played nearly 2 years of a nasty war in China running on assumptions, and I think I did a pretty good job, but there are some "fuzzy" bits. Here is my "interpretation", for lack of a better word:
All Infantry types are considered Front Line, remembering the special rules around Paratroops the first round they are dropped.
All Mechanized Infantry and Panzer Grenadier units are Front Line units.
All Armor Types are Front Line units. - Except, here is the first "fuzzy" area. What about StuG's? Assault Guns? Are the Front Line (they are listed as having Armor Effects, so my assumption is yes. They were used a Tank Destroyers more often that Support Guns, and Support Guns were used up close and personal like, anyway). Do they have an option? Could they be deployed as Support Units?
My assumption is that SP artillery would be considered Support Units, but again, I just a little unclear on this.
AA Guns and German 88's get a Special Mention:
Resolve Anti-Aircraft Combat
If the attacker or defender has anti-aircraft guns or '88's with an AA value, they may elect to deploy them in front line or in support anti-aircraft mode. An unlimited number of AA units may be deployed as support units.
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AA guns and 88’s may fire at ground units in the normal ground combat phase as front line ground units instead of deployed to fire during the anti-aircraft phase. AA guns have a defense value of “3” and 88’s defend in ground combat with a value of “6* or less” (and 88’s are considered AT guns when inflicting casualties.
And that leads me to believe that AT guns are Front Line Units, as well.
All Artillery are Support Units (with the confusion about StuG's). Does that count Katusha's as well?
It is my suggestion that you put together a small chart, in the Ground Combat area of the rules, laying out which units fall into what category, and listing any "either/or" units you wish.
PS: I want to state how much I REALLY like this combat system. It solves a number of problems with the A&A "Dogpile" combat, and incorporates several really nifty combat options from the Europa style of combat, without going to the 3:1 combat charts.