What's the point in running the campaign in a pre-plate era if you're going to allow players to have that level of defense anyway?
A few reasons, actually.
Firstly, the setting is intended to be an analogue of about 12th century Europe.
Secondly, it would be an aesthetic consideration that plate armour be removed as an option. So it's not an isuse how of much defense is being offered - but what kind of defense.
Either way, the thing is that plate armour shouldn't be available in 12th century Europe. I'm not removing plate armour because it's too good for the time frame, I'm removing it because it doesn't fit.
Besides, with my idea, you get a max DR of 10 (7 from the new armour, 3 with a visored helm with coif). Plate armour has a base DR of ten - not including a helm at all.
So even with this new armour addition - characters wouldn't have quite as much DR as someone in plate armour.
The changes you've suggested make a fully-mailed warrior nearly as invulnerable as one in the plate armor that you're removing from the game.
Nearly, yes. But only if he's fully decked out for battle in the best helm, with a coif, with a hauberk and chausses.
That seems to fit, in my opinion. Most people won't be running around in that kind of battle dress all the time - only when real battle is about to be joined.
I don't run my games like D&D, where your typical Fighter sleeps, eats, and goes tinkle in his plate armour.
So I think it's fair that a full battle harness be quite powerful.
I think you're overvaluing the effectiveness of mail a bit. Granted, the stuff has been around for a very long time in one form or another, but that's more because of its efficiency than its raw protective value. Breastplates are even older than mail, but they fell out of favor in the Iron Age because they required too much inflexible mass to stop iron weapons; mail was not as protective, but it was pretty good and allowed better maneuverability.
On the contrary, I think mail is undervalued of late. Too many hear about how mail didn't protect well against X or Y - and that sort of tends to devalue mail to a lot of people. But it was excellent protection for hundreds upon hundreds of years. And it makes sense that in a setting where the best protection is mail - that mail actually be worth wearing over other armour types (to explain its dominance).
I'd vote that you leave DR values as they are, and let your players be careful. If you're worried, reduce the AP value of certain weapons by 1 point and disallow others; or limit the strength inflation and feat/maneuver combo madness that Conan games can suffer, so as to prevent brawny guys getting one-hit kills on everything they meet.
None of these were concerns of mine, actually. I wasn't trying to 'replace' plate armour, because in my experience players rarely use it anyway in Conan.
I was just adding a couple logical armour choices that -did- exist, and I thought should be included in the game for the sake of completion. Knights did wear mail coifs underneath their helms - I wanted the game mechanics to reflect a reason for that. Chausses -were- worn to protect the legs, I needed mechanics to reflect that.
Flavour is all well and good, but it tends to be rather bland explaining that characters can describe themselves as wearing full mail coverings for their legs - but that it won't have any in-game effect on how well protected they are.
If it's horribly unbalanced - by all means we can discuss that - and try to fix it. But if your issue is just that I've "replaced" plate armour with more mail add-ons, then that's not something to worry about.