What seven would that be, and what would decide where an existing Pokemon would get placed?
I knew someone would ask that next.
To be honest it’s not even so much a revision of the current type chart as throwing it out altogether and starting from scratch. Sort of a “can I just do this completely differently?” thought experiment, which probably has to go along with massive changes to how we do status effects, PP, accuracy, and several other things (including doing away with physical/special). Pokémon don’t even have types at all, they just have weaknesses and resistances to attack types (of which attacks can have one, two, or even none), and those are assigned case-by-case.
Grass, Bug, some of Ground and a little bit of Fairy (Razor Leaf, Silver Wind, Earthquake, Moonblast, etc) all get condensed into “Nature,” which contrary to how the type chart works now is actually strongest against mechanical, pollutant, and spirit Pokémon. Water and Ice can be combined into one quite reasonably, if you don’t mind ditching “Grass beats Water,” which was never terribly intuitive anyway. Fire and Electric both fall under a single “Energy” type; attacks that use electricity would just have specific advantages against Pokémon that are currently flying or swimming (which are things Pokémon do, not things that they are). Fairy, Dragon and some of Dark (Dark Pulse being the main one) can be collapsed into “Magic,” best against Pokémon that rely on physical strength; Psychic, Ghost and some of Fighting (Focus Blast, Aura Sphere) into “Spirit,” most effective against Pokémon that rely on malice or anger. And then two “physical” types, and I go back and forth on what I actually want to call them, currently thinking “Might” and “Finesse” but the gist is that one is about overwhelming strength (Take Down, Crunch, Submission, etc) and one is about precision (Slash, Air Cutter, Pursuit, Twineedle, etc).
A lot of Pokémon would interact very differently to the way they do under the current system, and some Pokémon that now have the same type would wind up with different sets of weaknesses and resistances (like Meganium – resistant to Nature and Spirit, weak to Energy and Finesse – and Sceptile – resistant to Nature and Finesse, weak to Energy and Might), but I think this still gives you just enough to express something of the personality of every species that currently exists.