Let me preface this by saying I've never done a knife or machete build, nor have I tried versatility, so this will definitely have to be checked by some people that have done more research and experimentation than I.
Jason Liang Right off the bat I'm thinking this character needs to use machete's (main hand), SMG (off hand), and also have the ability to use throwing knives with the various different poisons (throwing). The stat distribution I end up with is
Strength: 7
Dexterity: 10
Agility: 7
Constitution: 3
Perception: 3
Will: 5
Intelligence: 5
Strength 7 to get to decapitate and be able to use whatever machete you please, Agility 7 for Sprint and eventually fancy footwork, dump Constitution and Perception, 5 Will for Ripper, 5 Int for Cheap Shots and Expose Weakness. When it comes to skills, I'm thinking you forget about crafting weapons and armor and just focus on grenades and knives, as your main hand is going to be a Katana, and it's not worth taking crafting just for the SMG. Plus, Rathound Regalia and eventually Shadow Dancer are more than adequate, especially on normal difficulty. IDK how tough it'll be getting through the early game with an uncrafted sword, so you'll have to ask someone here who has actually played such a build. Also, since you talked about self buffing, Temporal Manipulation fits in nicely with everything you're gonna want to do. In the end, I came up with this at level one.
Throwing: 15
Melee: 15
Dodge: 15
Evasion: 15
Stealth: 15
Chemistry: 15
Bio: 15
Temporal Manipulation: 15
You can do a lot of min maxing with Chemistry and Bio. Getting enough chemistry to make MK III Grenades should be fine for a long while, and the Bio is really just for drugs and making different kinds of poison throwing knives, so it can also wait till later and one can stop at specific points. You could also opt to go into electronics just so you can make an okay taser. I left out traps, lockpicking, and hacking, because you said the character is more of an assassin not a thief, so I figure that would suit the theme of the build a bit better. Where things get tricky is the feats, and frankly someone else will have to help you with all that. Off the top, some vital or really good feats would be,
Versatility
Cheap Shots
Expose Weakness
Ripper
Decapitate
Sprint
Fancy Footwork
Recklessness
Nimble
Psycho Temporal Acceleration
Pinning
Fatal Throw
Split Spare
Opportunist
and to make the SMG work, I would think,
Spec Ops
Full Auto
Commando
and I'm sure I left out a ton of other shit. Good luck to whoever tries to fine tune this list of feats.
The way I'd assume this build would play out would be to stealth to where you want to be, and start combat off with a good grenade and SMG burst at a big group of enemies, keeping people crowd controlled with poison throwing knives + nets, and than finishing off the low health remnants with the sword. IDK how well this will actually work, but it's normal, so I figure it shouldn't be toooo bad. This is a rough idea, and I'd recommend getting some fine tuning and feedback from other people on the thread that have actually messed around with SMGs and Swords.