I'm happy enough with my new mutant to share:
St:16 (20), Ag: 18 (20), To: 19, In: 18, Wi: 18, Eg: 14
Carapace, Double-muscled, Triple-jointed, Multiple Arms, Heightened Quickness, and you're short 4 points (I went with brittle bones, but it's a pain when you get to Golgotha: the shortcut did 184 damage with a rubbergum injector. Glad I gained too much xp doing other stuff before I went there). Maurader for +2 St and axe skills. Carapace, sprint, and heightened quickness, and okay toughness make it easier to survive. Triple jointed lets you get the dual-wielding skills (probably all but the last one) while giving you a chance to re-use sprint or flurry, and Double-muscled gets you the axe skills and keeps your penetration values at max while giving you a source of stun. Add stopsvalin or other bucklers to your 4 wrist slots for more stun (if you buy the skill). You'll get faces from your axe skills to improve your ego (add a knollwood skull, and you'll be fine). High enough int for even a mutant to buy skills and tinkering, but I put in an attribute point early and still relied on water ritual to get me a few skills (cooking, wayfinding, tinkering, shield, but no luck on trash divining this run). I'd love dual wield from Bey Lah, but waiting to find Kindrish or a lucky rep increase isn't great for a 4-armed character, and you have to solve the theft in a particular way.
I had no luck with baetyls, but cooked my eater's nectar and got lucky (cooked injectors are 25% chance at increasing all six stats by 1 which beats the 100% chance of +1 random stat or a mutation point). I also found a somewhat-early +3 ego face on a legendary Putus Templar just outside of the Stilt.