Cell wars isn't perfect in it's current form, but I don't think changing to a ratio is any better. Yes, this would prevent stinky poopoo 3v10 cell wars, but also all the way up to 3v17 cell wars, which isn't an unreasonable ratio. Try changing the ratio, and you will still notice unbalance at either the lower or higher end of it.
First off, I don't think fairness scales linearly when talking about number of people on each team. 1 guard vs 6 reds is quite more manageable than 3 vs 18, despite being the same ratio. Doubling the amount of reds certainly doesn't exactly double the likelihood they win (it's more than double), even if the amount of guards is doubled as well. Once the group of reds is big enough, you not only need more blu firepower to match the larger crowd, you need enough blus to fulfill the roles that a warden can't do all by themselves simply because they are 1 person in 1 location, such as having at least one guard behind the group of reds at all times, at least one guard ready to be disposed at an alternative getaway spot, and enough guards that you have some leftover for other minor roles like killing a rebeller in the crowd without freehitting, or shooting a door button that a red keeps +using. I didn't mention having a guard glued to the warden for protection, since that's more of a luxury.
Secondly (and more of a nitpick), I see the enforcement of this change leading to arguments, because even though this is simple math, it's harder to keep track of how many reds AND blus were alive at the START of the round and note the ratio than just keeping track of the blus, which already causes confusion when people tell the warden that the round started with 4 blus and he can't do meatgrinder.
Problem with changing to a ratio is that it holds the number of reds to too high of significance. 4 blus instead of 3 could easily be the difference for not needing cell wars to control the reds, but it feels a little silly to say that in 3v17, the blus can handle it, and 3v18 cell wars is justified. In the end, the blu count is way more significant since there's a static number of roles that guards need to fulfill in a round where rebellers exist, and it's rarely ever about needing more guns to ''match'' the number of reds you will need to shoot.
"what is this scooty fellow yapping about"