I'd prefer to avoid repeating previous themes and motifs, ideally the whole Pokemon-paradigm if possible. Rather than magical creatures being the norm, they could become an element of the storyline's escalation. In terms of the designs of the Beyblades themselves, I've previously mentioned that I'd like more customisation options that look better together; one way to achieve this would be to separate the marketing identity from the parts, in a fashion. They did this, to an extent with Metal Fusion, where the Energy Rings and Facebolts were the only part designed to convey a specific character, and the rest were effectively generic parts that didn't confer any specific identity on the Bey. HMS had the Advanced set, Striker, Guardian, Eterner and Averazer, which were built around the type of Beyblade rather than the gimmick or a particular Bit-Beast.
To this end, I'm thinking they could replace the concept of a particular series, like Dragoon/Pegasus/Valkyrie, with different manufacturers, each with their own unifying theme, gimmicks, motifs, and colour schemes, similar to the weapon manufacturers from the Borderlands video games, if you've played those. Parallel concepts like magical creatures, human characters and their battling styles can then be layered on top of this to create more unique marketing identities.
One of the reasons I would favour a system like this, is because previous systems have tended to match particular gimmicks with specific characters and colour schemes, with only a small number of truly generic parts, like the SG Flat, Semi-Flat and Sharp Blade Bases from the plastic generation for example, and I think that in addition to the issue of potentially getting a Bey with a part that has little or no competitive or aesthetic value, it also creates a disconnect between the fantasy and IRL elements of creating a combo. (a form of ludo-narrative dissonance, if you will) IRL you're not going to take your home-made, bootleg parts to a tournament, but in the manga/anime there are guys with parts that literally nobody else on the planet has used, or will ever use. I think this also helps to make sense of power-creep, because these manufacturers are competing with one another for market-share. (I also dislike the idea of a magical evolution of what is essentially supposed to be sports equipment, I think the purchase of new parts and and construction of a new Bey in the original series made vastly more sense)
Alternatively, I wouldn't mind seeing a series that takes inspiration from more mundane places, like series of Beys whose parts are designed with motifs derived from stationary, jewellery, fashion, gambling, vehicles, etc. Consider a flat rubber tip designed to resemble the eraser on a pencil, or a tip with a mode change gimmick that works like a ballpoint pen. Perhaps a spin-stealer with rubber contact points made to look like a large tyre from a tractor or a monster truck. How about an attack type with contact points made to look like cascading dice, battling in a stadium that superficially resembles a roulette wheel? I think there are a lot of places where you could look for inspiration that aren't the same rehashed mythological creature/pocket monster, that would still be rooted sufficiently in the elements of popular and historical culture that they would be identifiable to people and mean something to them in terms of characterisation.