One day, I hope to actually play DnD.
okay so, you basically reverse the mechanical formula for weaponry and armourHmm, I'm not 100% sure I follow. First, who would have the static attack value? Is this a thing where everyone has an AV, and you roll against it to defend, but not to attack? I'm cool with that idea, although I'm not sure about the knife example. Or am I completely misunderstanding you (which is quite likely).
so in 5e a weapon's to-hit is [dice roll]+PB+Modifier, and an armour's AC is [static value]+Modifier(other than heavy armours), right?, so weapons functionally have a modifier on every attack roll and AC is a fixed set value
my suggestion is to swap the weapon's [dice roll] and armour's [static value] to make weapons with [static value]+PB+Modifier and armour with [dice roll]+Modifier, each weapon you have ends up with a fixed to-hit value (a longsword might have [fixed 8]+PB 4+STR 5 and would thus always attack with a to-hit value of 17) and you make a dice roll when attacked to determine how well you defend yourself, getting a nat 1 to defend is the equivilant of attacking someone with a nat 20.
the fixed value in the new weapon formula represents how some weapons are easier to hit with than others (rather than 5e's fixed value of armour representing how baseline effective certain armours are at guarding against damage), like i was saying before, knives are classically weapons that are good at slipping through defences and tridents have (theoretically) have triple the chance to hit than a single pronged spear so they might have a higher [static value] in their to-hit formulas, while there would be some variance in the [static value] of weaponry it would be a much narrower range than 5e armour reaches over