If I was to make a roster, I truly think about who would be worthy of being playable.
There are three things I want form a playable character in a platform fighter. Mobility, Arsenal, and Combat.
Mobility: I'm not just talking about being quick and nimble. The character has to have something that can propel itself anywhere, especially upward. Either a skill(the SMB2 Super Jump, Cammy's Cannon Spike/Thrust Kick), a Power-Up(the S3&K Electric Shield, the Hi-Jump Ability) or an item(Proto Man's Proto Coil, a Jetpack) can work for many. This is primary why I'm having trouble thinking up something for Simon Belmont, and would rather choose R