Hi, I'm new here and I've been putting the attack type coverage calculator to good use. One of the things that's bothered me though is the presence of the Mega Evolutions and Pokémon not present in previous generations, like Generations 2 and 3.
As of the time of writing, you're only allowed two filtering options: Generations 2 to 5 and above. To the vast majority of users here this is more than enough, but to the ten or so people that like to stick to the older generations the results can be skewed. To clarify: The difference between total Pokémon between Generations 2 and 5 exceeds 200.
Here are my suggestions:
Add the option to toggle Mega Evolutions on and off.
There are a lot of them, and in many tiers they aren't present. This is particularly true for older Gens.
Add the option to toggle each Generation on and off.
A checkbox system would probably be the most effective in this case. When a Generation is unchecked, the Pokémon that made their debut in that Generation don't appear and don't affect the results.
And two bonus suggestions to really seal the deal. These ones are probably a lot harder to pull off though.
Add the option to input your Pokémon's Typing and show what it's weak to, in addition to what Typing is super effective against what your Pokémon's Typing is weak to.
I very badly yearn for a feature like this, where you can input what your Pokémon's Typing is, and be suggested what kind of coverage it needs most. This would make it trivial to tell what coverage holes need patching and for example which Hidden Power to pick.
Add the option to check and uncheck every individual Pokémon.
This one I can tell would be a pain to code in, but with additional features like filtering by Tier (UU, OU, etc.) you're looking at a very powerful tool indeed.
The calculator this site offers is the best out there right now. It's also the most intuitive. I think there's room for improving still and would like to hear what you think.