Combat Math in Missions & Mayhem

Yeah, another math post about the mechanics of Missions & Mayhem. These (here, here, here, and here) get a lot of reads, but rarely much comment. I assume either that means people don't want to comment on something they're just reading about but haven't played, or else everything I'm posting seems alright to them so they have not much to say. Either way, there seem to be no egregious math that would elicit corrections so that's encouraging. 

I was reading Eric's thoughts on a single saving throw (Swords & Wizardry style). It got me thinking about the math behind my saving throw system, and the combat mechanics more broadly. 

Following d20 Modern, M&M has Fortitude (modified by Constitution), Reflex (modified by Dexterity), and Will (modified by Wisdom) saving throws. Originally, I gave each class lowering target numbers for each save, the way classic and advanced D&D do it. If you multiclassed among the various Heroic Classes, you took the best value. But then when I started adding Advanced Classes in the campaign modules, I had wonky math going on. 

So, I've changed it to be more like the original. Now, each class provides bonuses to the die roll, along with ability modifiers. If you multiclass, you just add the new modifiers to your save values. 

Unlike the original D&D saves with different target numbers depending on the type of save and your class/level, or the d20 system that I'm riffing on which had varying target DCs for different types of saving throw, there is one constant and unchanging save target number: 16. 

This gives someone with no bonus (average ability score and no class modifier) a 25% chance to succeed on any saving throw. 

Combat, for comparison, uses ascending AC with the base AC as 11. So rolling a flat d20 with no bonus to hit, and the target has no armor or Dexterity adjustments, and no situational modifiers, you have a 50% chance to hit. 

These numbers seem like a good base to work from for me. 

It also means that area of effect attacks (spray autofire, grenades, etc.) need to hit AC 11 to affect the appropriate area. There's a "grenade bounce" check to see where the effect actually lands on a miss, which still might affect some of the intended targets. And then the targets get saving throws to avoid or mitigate the effects. 

Again, the math works well, giving I think, fair odds for combats in the game.