Xliest no it's an all or nothing deal now.
The downside of giving each individual unit a chance roll is that SWs will die on every attack, statistically guaranteed (it's rolling a 5 sided dice, if you do it 1,000 times then you'll land on each side 200 times). And when using Surrounding strat, half of all SW will die in every attack (flipping a coin chance just means half your units die every time). Or maybe not die, but be exposed to damages / fail hiding... Technically we wouldn't even need to run a roll for each unit, it would be simpler to just set hard limits like only 75% SW hide at all times, practically the same thing.
So people can enjoy high chances of total success with current system, or guaranteed losses on every attack (but is more reliable to know how much you will be losing on average, no surprise big loss).