>Dugtrio
It should correspond with how many dugtrio or diglet you currently have in your party.
For instance, you have 2 dugtrios. You can mega into 6 diglets or dughex. You have a dugtrio and a diglet, you'll mega into 4 dugogon. The scaling will be double or +1/3 Depending on what iteration you have and how many you have of it.
>Max mega is 6 dugtrios so 18. It's name would be dugoctodecio
Literally just a mass of 18 poops, each one taller than the next, coming out of the ground.
Also, this will introduce a new mechanic into the game where you can mega evolve your initial pokemon by a new evolution, ultimate evolution or maybe something like alternate evolution. From this, pokemon that had popular base or 2nd (if there is a 3rd evolution) will be given a mega-evolution.
>Pikachu, Cyndaquil, Fennekin, Dewott etc.