So, while downloading Shinobi & Samurai from Taxidermic Owlbear website I found they have a couple other games. 

Sort of. 

The Gothic Age is kinda not a full game.  Technically, it is, but only if you want to play a fighter and nothing else.  The "game" feels more like a combat experiment. 

http://taxidermicowlbear.weebly.com/downloads.html

With that in mind, here is what the combat is like in this version of D&D rules.  I think it's pretty interesting.

1.  Wisdom is gone, replaced by Agility.
2.  3-18 attributes are gone, now 1-5.  Attributes are rolled as 1D6, but 6's are re-rolled.  No charts needed, as your attribute is your dice modifier. 
3.  Agility adds to your defense.  Yes, you can be a "dodge tank".
4.  Leveling up means one random attribute goes up by 1.
5.  Gear have quality ratings, including two grades of negative/bad that subtract from your combat roll if you have a low quality weapon.
6.  Weapons have traits like 5E.  A long sword is +1 to your defense, but big two-handed sword crits easier.
7.   Armor boosts defense by 1-5, but heavier armor limits Agility bonus.  An agile player may be better off in lighter armor. 
8.  Armor and weapons can be reduced in quality by critical hits.  There is a table for what a crit does, usually your gear gets reduced, to more severe things for rolling a 2 or 12.   
9.  Hit points are fixed.  3+Con.  Aka 4-9. 
10.  All weapons just do 1 HP of damage.  Critical hits can do 2 (depends on the roll on the crit table). 
11.  Combat is 2D6+attribute vs 2D6+Defense (armor+Agility).  Attacker wins a tie.  In other words, a static Armor Class is gone. 

That's a lot.  Hell, just ditching the D20 is weird, but going to an opposed roll system and Agility being a big factor makes me happy. 

I like it.

That sounds interesting.  Opposed rolls, and the attacker wins any ties.


I could go for a tie dealing half damage.

The thing I like best is the 5E weapon and armor traits. 

Like a short sword is "light" and "versatile".  Light means you can use either strength or dexterity as your bonus.  Versatile means you can use it as a throwing weapon. 

Chainmail armor provides a defense of +4, but Agility bonus is capped at +1.  If your agility is a 3, you will have a defense of +5, but wearing leather armor is also a defense of +5, but costs a lot less and is cheaper to fix if damaged.

But, you can sacrifice armor points instead of hit points at will.  If your constitution is low, then maybe chainmail is a better choice to survive longer. 

Those 5E type features are good ones, and I'm ok with games copying them.  It's one of the reasons I like Olde Swords Reign.  It has them. 

I mentioned combining this with a magic system to create your own RPG basis, and then I remembered something.

The game that originally drew me to their website was Shinobi & Samurai, which has an expansion book.  In that book there is an optional magic systems based on using energy points instead of spell slots.

I think that would be all you need to have a complete game.

Here is the question.  If you change that much about a D&D based game by this extent, is it even D&D anymore?

1 to 5 based stats (yes, its 1D5, so re-roll any 6's on a 1D6)
Wisdom is replaced by Agility, so four physical abilities, and only two mental.
Fixed hit points (your CON ability, no more, no less)
Opposed Rolls for combat
Armor that can be damaged (aka: sundered), reducing its ability to protect you
Magic based on energy points.  Re-cast anything you know until you run out of energy (optionally you can use your own hit points as energy if needed)

At that point I would have to say that is is NOT a D&D based game anymore.  If the only thing that the has in common with D&D is the name of some (but not all) of your core stats (STR, DEX, AGI, CON, INT, CHA), then its a fully new game.

I may have to do this.

Welcome to my world.

Several years back I'd realized my system mechanics were so different from D&D that the only thing still tethering it were a couple bits of terminology and access to the familiar bits of D&D lore included in the SRD (colored dragons, its set of demons/devils, medusas as natural humanoids and gorgons as bull-like beasts, rubbery green trolls, etc. etc.).

So, having already changed a lot of the base lore anyway, I decided to abandon the OGL entirely and, in the long run, my system and world lore was healthier for it. Going back to first sources for monster lore or having to use my own ideas kept it from feeling like more of the same.

So, yeah, I say DO IT!

I'm thinking warriors and combat from The Gothic Age, Rogues from Shinobi and Samurai, and wizards from Shinobi and Samurai Companion. 

I might even rename all the weapons and armor to Japanese equivalents.  Spear = Yari, 1-handed flail = nunchuck, long sword = katana.

I might want to contact taxidermic Owlbear and see what they think.