Carts can only exist between $8000-$BFFF and $D500-$D5FF.
There's 13 address lines supplied which allows 8K of address selection.
The S4 and S5 lines allow selection of the upper and lower 8K of the cart address space.
The CCTL line allows selecting the $D5xx addresses.
Not possible to do tricks like a blit into colour registers etc.
The banking scheme if present is decided mostly by the cartridge - and is within the realm of possibilities above.
Most banking and control schemes simply use the $D5xx addresses in some way. In some cases any access type, in others an access or write to particular address range, and in others a bitsetting to an exact location.
Also we have modern day flash carts. In most cases they use writes to specific addresses in the ROM area to initiate wrtite block sequences. You can look up datasheets for some of the chips used and correlate what needs to happen on the Atari side from them.