Who could replace the actors that have passed away?

Gary Owens (Cmdr. Ulysses Feral)
Brock Peters (Dark Kat)
Keene Curtis (The Pastmaster)
Roddy McDowall (Lenny Ringtail/Madkat)
Linda Gary (Dr. Abi Sinian)
Ed Gilbert (various characters)
John Vernon (Rex Shard)
Robert Ridgely (Dr. Harley Street)

For Cmdr. Feral, I've heard Tom Kane suggested, which is kinda fitting since he does a pretty decent Gary Owens impression (listen to his voice for Prof. Utonium). I often imagined Clancy Brown as Feral.

Hmm, Dark Kat. I imagine either Kevin Michael Richardson, Kevin Grevioux or Jonathan Adams.

Robin Atkin Downes is who I see as voicing Pastmaster.

Tom Kenny would make a good Madkat.

Dr. Sinian, I'm stuck on.

Don't recall Ed Gilbert doing anyone fairly significant (aside from Tiger Conklin and the occasional Enforcer).

Shard is another role Clancy Brown could take.

I always thought KMR was imitating Ridgely when he voiced B'wana Beast on Batman: The Brave and the Bold, so he might fit here.

Thoughts/suggestions?