Super 7 would be a great avenue but they inexplicably keep doing inferior versions of “regular” characters.
The G1 Unicron toy prototype design they did was very popular. You'd think they'd take the hint that the money's in more out there ideas.
But, as has already been mentioned, budgetary concerns tend to be the overriding concern in this business, and we as fans on the outside will never be fully in the know about what kind of compromises and cuts have to be made.
We don't have day to day stuff at our fingertips, no, but Hasbro's teams do share stuff with us.
I remember when Hasbro, way back in the day, explained that the reason for the Energon combiners only having two limb moulds each was budgetary. The budget would allow for either two combiners with four limb moulds each or three combiners with two limb moulds each. They made the choice to go with the latter, thinking fans and kids alike would appreciate more characters.
That was the first time I really re-evaluated how I thought about this stuff. It's easy to fall into the trap as a fan (especially in one's younger years) of assuming Hasbro's doing stuff for some malicious reason. But when it comes down to it... the design teams are people passionate about their work and the brand, and they want to do cool stuff. Sometimes the money is what it is, and they have to make decisions about what kinds of cool stuff they have to forgo to do other cool stuff.
Like... I don't think anyone on the design team is currently sitting in their offices in Rhode Island going "stupid Pretenders. Screw those nerds! They'll take a hovercraft with a shark fin on it as Finback and like it!"
No. It's that Pretenders are a REALLY difficult concept to pull off given the economics of modern toy engineering. You're looking at two separate toys, with two separate sets of tooling, that all have to be fit into one budget. And then we have to ask... how articulated are these Pretenders gonna be?
Combiners, Head Masters, Titans, 80s music and storage medium alternate modes, all of this stuff proved viable at retail in the modern day but Pretenders is the one gimmick from G1 that's just too hard to make work.
Of the "fusion" style Pretenders Legacy has given us, I think Bomb Burst, Iguanus, and Bludgeon came out pretty nice. Skullgrin didn't work, but 3/4 isn't a bad batting average.