We have the Dark Synchro and Token templates which will work somewhat for this, but could there be a way for the cardmaker to allow us to create custom card types? Probably like its own little section in the cardmaker where you can select a color for the cards to be, then check whether or not the card uses Spell/Trap symbols, has Levels, has Level-stars-but-on-the-other-side, etc.
What exactly do you mean with "color for the card to be"? This could namely refer to selecting the Spell / Trap border for a monster, for example. But could also mean that you want a palette from which you want to pick any random color, like green, brown or baby pink. The latter option will most likely have its own share of issues: does it need a galaxy (xyz) or honeycomb (link) pattern? do those types have pendulum support? and so on. Lastly, there is the option of giving the user the ability to upload the relevant images for border, star, spell/trap icon, etc.
The first and last option should be doable, but a reasonable amount of reworking will be needed. So it will take some time before such a feature gets implemented, assuming the rest of the community feels the same way about the need for such a feature. Then there is still the issue of how different settings will interact with eachother (Link markers and pendulum parts), and whether the card maker will be responsible for making it a pendulum border.
Also, you already have the option for the stars to appear on the other side of the card, by providing a negative number. Xyz and Dark Synchro just flip the sign behind the scenes. I don't quite see why you'd want that with the current templates, but the option is there I suppose.