If you were in charge of organizing the Omnitrix’s alien catalogue, how would you go about it?

In my opinion, I think the logical thing to do would be to sort each species by affinity/anatomy. Some examples below.

[Heat and Radiation-Based]

Pyronite (Heatblast)

Methanosian (Swampfire)

Prypiatosian-B (NRG)

Unknown (Atomix)

[Aquatic and Water-Based]

Piscciss Volann (Ripjaws)

Orishan (Waterhazard)

Cascan (Overflow)

[Electricity-Based]

Nosedeenian (Buzzshock)

Transylian (Frankenstrike)

Cerebrocrustacean (Brainstorm)

Amperi (Ampfibian)

Gimlinopithecus (Shocksquatch)

Conductoid (Feedback)

Fulmini (Shock Rock)