Your problem is that you're mixing up tactical and operational things together. C# ground combat does not model operational level at all, only tactical level - where each formation shoots at each other. At the tactical level, an infantry platoon is not going to protect an artillery battery at all and no army organizes itself in that manner. The gunners are on their own - infantry protects artillery by preventing the enemy from ever reaching the artillery in the first place - but that's operational level and Aurora doesn't do that at all.
You don't have to just break through to hit support and rear echelon forces. Attacking forces have always a chance to hit the rear and echelon their size just count for less
Yes, exactly as I said in my post and the quote from Steve. But both Support echelon and Rear echelon units are counted significantly smaller than their real size. I gave you numbers and all.
That usually means that putting infantry in the support section will increase the chance of them being hit in the first place every round
Not really because the difference is so huge - 25% for Support echelon and 5% for Rear echelon. Sure, going from 100 tons to 125 tons is an increase but if your Front echelon is 15 units each 1200 tons or more, then the odds have not really been changed in any significant manner.
If you put them in the front they actually protect the rear and echelon allot more
Yes, this has not been in dispute and it's how it should be.
Even if you can make a formation 1/5 less likely to attack that does not make infantry better in the rear as they still protect better at the front.
That's a different argument and different calculation - you're mixing two things together that should not be mixed together.
The only reason for using small garrison platoons in with your artillery formation will be role-play the way I see it...
Yes and not much of that either because AFAIK no army puts "garrison platoons" with artillery.
If we instead could put a few platoons of infantry to protect the artillery and make it allot less likely the artillery is hit instead of the protecting platoon, like a 1/10 chance to hit the artillery instead of the infantry platoon, then it would make sense to attach some infantry to defend the artillery.
I think you've been carried away by your own argument. There is a reason to attach PWL/PW infantry to artillery, but that reason isn't so overwhelmingly strong that it would be mandatory.
I'll repeat the mechanics here because I have a feeling that people have forgotten how it works. There are two, entirely separate calculations:
1) The odds of each enemy formation attacking your artillery formation
2) The odds of attacking enemy formation firing at your cannons instead of anything else inside your artillery formation
So first, let's look at the odds. I'll use Steve's WH40k units as examples. His IG Brigade is 5268 tons, whereas the four regiments are 6738, 5546, 6882 and 8942 tons respectively. And remember that Steve's brigade includes HG and AAA units in addition to artillery, plus some guardsmen and supply trucks. A pure artillery unit would actually be slightly smaller. The regiments will be in Front Defensive echelon while the brigade will be in Support echelon. So when each enemy formation rolls for target, they choose between:
8942
6882
6738
5546
1317 (that's 25% of 5268 tons)
I'm not sure how exactly Aurora does the calculation but I'm going to assume that it's similar to how internal damage is allocated in a ship, meaning that all component sizes are compared to each other and then a roll is made against them. The easiest way to illustrate this is with an Excel chart:
You can see how vanishingly small the odds are that the support brigade is going to get hit.
Now we get to the second calculation. Still using the same example, we get the following sizes:
36x artillery 2592 tons
12x anti-air 1176 tons
2x headquarters 1000 tons
100x infantry 500 tons
AFAIK, the attacking formation then has each of its constituent units shoot at the various units inside the defending formation and the calculation is done in the same manner, leading us to this:
The 100 Guardsmen Steve put into the Brigade isn't going to make much of a difference, true. But we could double their size without really affecting the first calculation. In fact, if we increase the infantry five times so that it matches the artillery at 2500 tons, that's still only an increase of 500 tons in the first calculation - not much of a chance there.
Summa summarum - I don't think that you should worry about it. It is far more important to avoid your Support and Rear echelon units getting hit in the first place but if you want to play it safe and have cannon fodder/meat shield protecting your artillery (or other high-value units) then you can do so without significantly increasing their risk of getting hit in the first place.