My bias is showing here, but Euro g1.5 is exactly what I want to see. Thunder Clash and Flash, but also Pyro and Clench, and Skyquake and Stalker, etc. Core class non-springy versions of the flipchangers, and the cyberjets too. And then a capsule of Machine Wars redecos. I would be so spoiled.
No doubt there's enough there to FILL a line, but I'm sure we'll need more than that to make it a solid one. If anything, these characters are likely in retool/pretool territory (the only difference these days being who gets put into a wave first). "if we make x, who can we get out of it with a new head? Hurricane? Sure." I genuinely doubt Selects Rotorstorm happened any other way. Although an all new mold for him would be beyond dope.
Thunder Clash, though, maybe? There have been theories about reusing some of the Motormaster tooling (the trailer/base thing is a reach, but idk). And an all new mold has an Optimus redeco waiting to happen.
I'd also love for more Energon stuff -- if they're not going to retool Scraphook into racing truck Rodimus, just give me a new mold for it -- but the Energon weapons aspect in particular seems to have fallen by the wayside as an abandoned Legacy gimmick.
Which is probably just as well. It would be rough to have to track down all the campaign redecos Takara would do (Skids' axe in clear yellow! Elita-1 rifles in clear green! Arcee blades in clear orange!). Hell, all this time later and I still haven't found most of the AOE Legendary Weapons. But I'd probably try anyway, haha.