>>48500419Hoenn's dex has 202 Pokemon.
192 discounting legendaries.
Hoenn has 34 routes plus some underwater areas. We're ignoring caves/Old Mauville/other locations for now and focusing on the routes.
192 divided by 34=5.64
Round that up to 6, and you'd need 6 distinct Pokemon obtainable on each route to make every Emerald mon catchable in the grass.
However, if you want to include all 898 Pokemon
898 divided by 34=29.08.
Good luck fitting all those Pokemon into one region's grass.
Let's double the 34 distinct encounter tables by adding water encounters via fishing/Super Rod usage to every route to get 68.
898 divided by 68=13.20.
Now if every town and city (all 16 if you don't count the battle frontier or resort) obtained grass AND water, that's 68+(16x2)=100
898 divided by 100=8.98
If you want 6 distinct encounters per route and six different ones for water tiles, YOU WILL NEED ADDITIONAL AREAS.
Remember: If you're adding more Pokemon to a region, ALWAYS add additional side-areas with their own encounter tables.
Pic unrelated, I'm good with numbers.