Didn't think I could change my mind so much over the course of one day, but having weighed the options as best as I could... Grass/Dark Grass/Fighting Electric/Dark
So yeah, that's my order. Grass/Dark takes the lead when I considered Grass has better physical STAB options than Electric. Grass/Fighting is also interesting to challenge every weather starter bar Ninetails. After that, Elec/Dark (Pursuit still valid), Elec/Grass (for dual anti-water STAB and Water resist) and finally Grass/Dragon that I'm not a fan of (that x4 Ice weakness means it risks too much switching into common Water types that WILL carry Ice Beam for coverage).
It's been a great discussion guys. Good luck to all and may the best type win.