A while back I had this idea for a theoretical TTA reboot, and I came up with a (admittedly not creative) way to compensate for Messick's death by "replacing" Hamton--"replace" him with his little cousin--a brand new character. The in-universe explanation would've been that Hamton's father got a job offer in another city and consequently Hamton's family moved out of Acme Acres. Then along came Hamton's cousin (I still don't know what his name should've been), who moved into Hamton's family's old residence. Theoretically, Hamton himself could've made a guest appearance in a one-off "family reunion" special ("I just got a letter from Uncle Wade and Aunt Winnie--Cousin Hamton's coming to visit!").
Obviously this is one of the most common reboot/sequel tropes/cliches--characters suddenly having siblings, cousins or other relatives that weren't mentioned before just to compensate for the loss of the original actor. However, when Alaskey had died, I'd figured I'd have to have given Plucky the "little cousin" treatment as well.
For the record, I don't have anything against recasts, and they can work provided the right sound-alike is chosen, but consider this a back up plan. Just like with Disney's Rescuers Down Under, when Orville Albatross' VA died, several sound-alikes were tested but didn't sound convincing enough, so they decided in the end to give Orville a brother named Wilbur (just like the Wright Brothers).
But Hamton and Plucky certainly are important characters, and they're important enough to justify recasts. In the case of Hamton, one likely candidate for a sound-alike IMO is Jeff Bergman. Bergman was the original voice of CN's classic toon sister-station Boomerang, and his announcer voice is very similar to Messick's announcer voice that can be heard on so many classic Hanna Barbera cartoons. In addition, Bergman voiced many Messick-originated characters, such as Boo Boo Bear, for many late 90s/2000s CN and Boomerang promos.
In regards to Elmyra's being eliminated from the reboot, I wonder what the in-universe explanation for her absence will be. My theory was she'd be serving a life sentence in the Acme Acres State Penitentiary for her history of excessive cruelty to animals.