While they might have been neat to have around during Sonic Heroes like they were originally planned to, I don't think adding them into the Modern cast now will just clutter things up, unfortunately. This is not to say that the expansive cast of characters is a bad thing at all like many might claim, but Sonic Team needs to figure out when it's appropriate to use some characters in a story and when not. Just because Big the Cat existed when SA2 was being made doesn't mean he has to be an integral part of the story, likewise the same for Chaotix and Sonic 06, there is a time and a place for certain characters. Sonic Forces went way too far in having every (relevant) Modern character present even though the majority of them don't have much relevance to the plot at hand. In theory, it would be justifiable given they're all part of a resistance cell, but in execution, the only characters that really mattered outside the two Sonics, Tails, Avatar, Eggman, and Infinite, were debatably Knuckles as he was the Resistance Leader and Silver because it led to the Phantom Ruby Prototype being collected by the Avatar. You could drop the rest of the characters and replace them with NPCs and nothing would really change. In a nutshell, Sonic Team really needs better writers who know when to use characters appropriately and when they're just in the way of the story or standing around for fanservice. It seems to me he's trying to do damage control for the brand's lore at the moment and adding the duo into that side of the franchise is just going to do more harm than good.