First...foam weapons (melee and ranged). For the purposes of safety, these are slashing and bashing weapons, because they typically have some kind of rigid core and if you thrust with such a weapon the core could expose itself and literally impale someone. As an added safety function, head shots are either banned (with serious repercussions) or seriously deterred and frowned upon (in which case they don't count toward damage, but the players are mature enough to accept that accidents happen).
Secondly...the combat is fully enacted. If you hit with your weapon, your opponents takes a hit of damage...you don't suddendly stop things to see if that hit managed to get through armour, or how much impact it had. There's an honour system to this, but in conflicts pivotal to the storyline there mightt be 'impartial adjudication from an umpire/GM'.
I like the quick description of combat given towards the beginning of "Knights of Badassdom", where hits to the torso are worth 2 points and hits to the limbs are worth one point but you don't get to use that limb for the remainder of the conflict (or until some kind of healing effect takes place). As I type this, I can't remember the specifics, but that sounds lime a great place to start a Boffer system.
Since we don't want single shot kills, that means everyone needs at least 3 hit points (in which case 3 limb shots, or two trso shots will take a typical character down).
Actually, I think I'll change that core mechanism a bit, just so combat lasts a little longer and is a bit more dramatic.
Here is the absolute basics of the system...
All players get 4 hit points.
Torso/Centre-Body hits count as two hits.
Limb hits either count as a single hit, or eliminate the use of that limb for the remainder of the combat.
(Arm hit - lose access to the weapon/shield in that arm, One leg hit - may not move beyond a slow walk, Two legs hit - knocked to the ground prone)
Having fought on the LARP field, I know that limb shots are far easier to accomplish than centre-body hits, but someone who is a little tactical shouldn't find it too hard to get a torso hit eveery now and then (especially when flanking with two or more players against a single victim). It's not that the system rewards teamwork, it's more a case that real life rewards teamwork.
Then we can start considering armour or character toughness...perhaps a tough character might have one or two extra hit points. A single extra point doesn't do a lot against torso hits, but an extra ablative hit point to sacrifice might keep a sword arm active for long enough to turn the tide in a conflict.
Since we don't want to break the flow of combat determining whether armour has absorbed a hit or deflected it, I'm thinking that the best solution would simply be to give armour an extra hit point or two in the area where it is located. At the simplest level, leather armour adds a hit point to its location, metal armour adds two hit points. Locations are: Torso, Each Arm, Each Leg. Players can wear head armour (and are thoroughly recommended to do so), but since head shots don't count we don't need to worry too much about combat mechanisms and statistics for these.
In this basic set-up, we can handle gladiator style armour where a single arm is covered in metal plate (and maybe the legs have leather leggings)...a character armoured in such a fashion would favour blocking with the armoured arm, because they have a few extra hit points to waste as long as they get hit in this location. _(Most other forms of armour also seem to fit with the system)_
We don't end up with a lot of variation between types of leather armour, or types of metal armour, but this might be handled through out-of-combat effects...maybe each hit taken by armour permanently damages it until a repair effect occurs...high quality armour might be easy to repair, while crappy armour is always falling apart and needs replacing after each conflict.
This means our complete game system needs some kind of skill mechanism for repairs...Which in turn means that we might have specialist characteers who wander around with the troops specifically with expertise in armoursmithing (or magical repairs). These are services that can be rendered as a part of a trade ecosystem.
It's adding complexity, but the raw functionality of combat isn't impacted...so I think this is a good thing.