Simple scaling weapons and armor (ability overflow edition)

I've written about this before: here and here.

This is just a simplification, but I think I like it better than using tables. It is meant for 5e, but it was originally imagined for another system I'm writing (which is a simplification of 5e).

For the purposes of this post, we're using the expression "ability surplus" to mean ability-10. 

Score	Surplus
10	0
11	1
12	2
13	3
14	4
15	5
16	6
17	7
...	...etc.

We have two sample PCs to test this system.

Joe has Strength 13 and Dexterity 16 (i.e., an ability surplus of 3 for Str and 6 for Dex). 

Jane has Strength 18 and Dexterity 12  (i.e., an ability surplus of 8 for Str and 2 for Dex). 

Let's go!

Weapons

Most weapons add 50% of ability surplus (Strength or Dexterity) to damage. This is practically identical to what 5e does.

Weapons that use both Strength and Dexterity may add a combined 60% (minimum 20% each).

Composite bows, for example, might add 30% of each to damage. Both Joe and Jane would get a +3 bonus:

Joe: 30% of 9 = 2.7
Jane: 30% of 10 = 3.

Lets say heavy slings use 40% Strength and 20% Dexterity instead. Joe gets +2, but Jane gets +4:

Joe: 40% of 3 plus 20% of 6 = 2.4
Jane: 40% of 8 plus 20% of 2 = 3.6.

Turn the nobs a bit here and there and you'll realize you have endless possibilities. For example:

- Two-handed weapons has a maximum of 70% instead of 60%. They usually add +10% Strength.
- Versatile weapons used with two hands may add 10% Dexterity instead (I'm thinking quarterstaves, spears...).
- Off-hand weapons add up to 40% instead of 50%, and must use at least 10% Dexterity.
- Thrown weapons always need more Strength, ranged weapons more Dexterity.
- Magic weapons may add some Intelligence, Charisma or Wisdom to the mix.
- etc. etc.

Art by Rick Troula

Armor

Remember this system?

Here is something that can be even simpler. And more granular at the same time.

You add 100% of your Dexterity surplus to AC. Unarmored Joe has AC 16, unarmored Jane has AC 12.

However, that assumes you're carrying nothing. If you are carrying 20% of your encumbrance limit*, you can only add 80% of your Dexterity surplus to AC.

(*your encumbrance limit depends on what rules you're using... slots, pounds, etc. But you can think of it this way: you have a number of slots equal to Str, and +1 to AC takes one slot. So, if you have Str 15, you could carry three pieces of armor [+3 AC] and still add 80% of you Dexterity surplus to AC, but only if you're carrying nothing else).

Here is where things get interesting. Joe, who is quicker, gets more benefits form travelling light. Jane, who is a lot stronger, would benefit more from armor, since it would be less encumbering.

Natural armor is probably exempt, and magic armor is lighter.

The system only "breaks" if you're very agile and very weak: armor will actually hinder your AC. But this already happens in 5e. And, well, sounds quite sensible.

Of course, you do not have to recalculate AC every time you pick up a new item... But when you do, players will quickly realize that encumbrance matters.

UPDATE:

Here is another way to do it: use a table. This one, for example. So, if Jane has an "Strength B, Dexterity F" Greataxe, she adds +7 to damage.

	A	B	C	D	E	F
10	0	0	0	0	0	0
11	1	0.8	0.6	0.5	0.4	0.2
12	2	1.6	1.2	1	0.8	0.4
13	3	2.4	1.8	1.5	1.2	0.6
14	4	3.2	2.4	2	1.6	0.8
15	5	4	3	2,5	2	1
16	6	4.8	3.6	3	2.4	1.2
17	7	5.6	4.2	3.5	2.8	1.4
18	8	6.4	4.8	4	3.2	1.6
19	9	7.2	5.4	4.5	3.6	1.8
20	10	8	6	5	4	2