Okay, so I think I have worked out a system for determining if you should take an assistant coach for an upcoming match.

First, we go to the expected number of meaningful drives for the match, defined as a drive in which either team has a realistic hope of scoring. This can't be less than two, and expecting more than four is probably not a good idea. I don't know what the statistical average is, but I'm going with 2.7 if neither team can pull off a fast score, 3 if one team can and the other can't, and 3.6 if both teams have some hustle. If Overtime is possible, I add 0.6 to this: it'll be more added drives per OT if the teams are fast, but the score is slightly less likely to result in a regulation tie, so not knowing any better I'm just calling it +0.6 regardless of speed. These numbers are kinda fuzzy, and you may tinker with them. However, what's not fuzzy, is that we divide 216 (get all the dice out of the way) by this number to get the target number (N) for our RR value and net AC calculations.

Target number
Both teams slow: 80, or 65 with OT
One team slow: 72, or 60 with OT
No slow teams: 60, or 51 with OT

Then, we determine the value of an extra team re-roll counter for each side (we'll call own and enemy RR counters R and E). Since TRRs and ACs are all expressible in gold piece terms, I'm going to divide the default RR counter value (half a TRR) by 10k gold to get a number between 2.5 and 3.5, which we can just call 3 (because what matters now is if you need the RR, not what it costs), and adjust based on need. As a data point, "if I had another 100k in Petty Cash, I'd take Extra Team Training" is worth 5, and no bonus reroll on a meaningful drive is ever worthless, or at least you don't know it will be worthless in advance. RR in the second half or overtime are more valuable, so add +1 if overtime is a possibility.

RR value (calculate R and E separately)
Already got 8 rerolls: 1
Don't want more: 2
Got enough, but more is nice: 3
Wish you had more: 4
More would be a priority: 5
Desperate for RR: 6
Overtime could happen: +1

Now, we get to the current AC status. For each AC, compare to the current ∆AC to get a value for the added chance of winning the BC roll (W) or of not losing (T).

Current ∆AC: W, T
-3: W=3, T=4
-2: W=4, T=5
-1: W=5, T=6
0: W=6, T=5
1: W=5, T=4
2: W=4, T=3
for each additional +1: subtract 1 each from W and T.

Now, the formula for the value of an assistant coach is (RW+ET)/N. If this is greater than 1, another AC is a great idea. If it's less, it's not worth even TV, but situationally it could be worth spending the money on, if your opponent has to ready at +10-45k ahead of you.

In practice this means you should seriously consider an Assistant Coach if you think the game will be a shootout, or if overtime is possible and a 2-1 grind or some OTS action seems likely. Otherwise, it's less good, but if you have 20k petty cash and nothing better to do....

WDYT?