Neal .. let me take off the blue jacket for a bit ... it is just game player me. My regards to yourself- and hoping things are going just as well for yourself as they have been for me.

Last I heard you had Campaign Gettysburg -so I am going to assume that is still the title you are operating under - at the same time, "the artillery duel" - can may be seen as design intent -I'm not defending it, but I suspect, like you -I am trying to get a handle on what is what. The way I see it, is there are 2 forces at play here even before anyone gets to have a crack at analyzing things - that being what the engine (at any given time) will allow a scenario to do, and what a scenario designer's vision is - as J Tiller does the programming and a few other guys over the course of the series do the scenario designing. The other thing that you are up against (assuming it is Gettysburg) is that you don't have anywhere near the artillery ammo that the other side has -and they can shoot you up pretty much at will. Or in other words, it is as if you as the ANV player have to pick your spots -but at the same time receive it back at will and at pretty much any range -there is no discouragement to the Union player to have them think twice about taking any potshot with their artillery.
(To be clear too - I am only speaking in the context of the product - I know others have their own takes on it -and that is fine, but outside the scope of what I am saying).
It is also true too that there isn't that large of a scenario designing community that has looked at things in this level as there are in the other series. Frankly, it is really a lot of work, and then even more to try and get the right balance.
See, too another problem can be if you take the historical Antietam scenario in Campaign Antietam, there are a lot of fixed units -but nearly all of them have a 100% probability to release on a set time. While, I understand that mechanism itself is taking things out of the players' hands, in my mind, maybe it isn't taking it enough out of the player's hands to make things a little more of a game, and more interesting in the process (this is more my own scenario design philosophy - but with the disclaimer being I haven't actually designed any... ). It strikes me that the mechanic that was used in Richard Berg's boardgame 'Gleam of Bayonets' works maybe a little better and makes for a better game -just by making the release times a little more variable. If you have no release times whatsoever -basically what happens is that the Army of the Potomac has the Army of Virginia in a box .
Cavalry, I think is probably a matter of context - in that if you lose it in a linked campaign - most of it stays gone for good. But I understand where you are coming from. In Gettysburg as a stand alone scenario the Union player is probably going to try to get them out of the way ASAP, and use them to cover the flanks. But, point taken.
As for a definitive answer, -I'm afraid, that is something that only an individual scenario designer can answer for (most of which I have no idea where they currently are, aside from Rich Walker. Which means the only thing anyone can go by is the notes files in each title. I think I am allowed to post those files from the disks - I'll have to go back and check over my notes. I realize that not everyone has all of the games- and consequently they don't have access to the designer notes in the titles.