Although the mixed seed outcomes are interesting its easy to see limited outcomes when hitting the randomize; i feel like allowing for a mixed seed monster and the enviornment can really add to the encounters.
Just an off example if a campaign has goblins serving under the drow for some odd reason being able to mix the two in encounter calculation would help make the encounter a bit more interesting. Or like having a yuan-ti spell caster being guarded by orcs.
Also maybe adding a line to generate allies?
The generator has a fairly high limit for spawning and potential for an enemy army being generated.
Army creation maybe?
This may be a stretch but possibly allowing for a checkbox on whether or not to have spellcasting creatures or some with or without multiattack or status effects.
Most of this does rely on the dm themselves to makethings up but hey if we knew exactly what to put the party against we wouldnt be using generators.