Other people have said it better, but here's my thoughts on it. I agree with Arcus.
1d100 vs 1d100 is already going to give you a lot of variance. Adding explosive dice just means explosively increasing that variance. Which is all fine and dandy until peasants start killing dragons, Grail Knights trip over their own lances into skeleton spears, Abhorash goes out like a chump, and Skulltaker murders the entirety of the Empire's military. Of course, these are all hilarious exaggerations... that nonetheless become possible - if deeply unlikely - with exploding dice. You might be thinking of possible third order criticals, think fifth or ninth order. The sheer insanity of something like that regardless of skill or ability. That's what you open yourself up to when allowing explosive crits with massive modifiers.
My main concern is simply that characters and armies performances aren't representative of their skill. Up to a point that's expected: bad days, changing circumstances, shitty matchups, just messing up, all that doesn't stretch SOD and makes sense. But only up to a point. Not much of a problem here, where even though there is a ten point difference in martial (and Johanna was leading them), it's not unreasonable. In a lot of conditions, it's going to be similarly fine, but there will be other times when it isn't. For example, seeing someone defined as one of the best fighters in the Empire, nearing the limits of a mortal frame, with a name like 'Skullcracker' fail to make a difference against bandits raises a lot of pointed questions.
By all means, experiment with it some more if you want, but past experience tells me that allowing explosive crits like that, doesn't just invite more, it assures that you will reach that ridiculous point where they lose nearly all value by becoming expected, simply appealing to the part of the brain that likes seeing big numbers.
The 95+ rule is an excellent compromise, but even then you are probably going to see it much more than you think. It sounds interesting though, with a roll like that swinging battles.
You get an internet cookie, this made me giggle.