Migrating custom board to "Standard Boot"

[Patryk]

Hi
I've been working on a custom board based on NXP LS1028A and
considering migrating the boot flow to "Standard Boot".
The motivation to migrate to "Standard Boot" is that the current boot
setup provided by NXP feels a bit messy. Looking at the e.g. LS1028A
boards they support distro_boot mixed with runtime bootcmd override
based on TF-A boot source detection.
For example, if the platform booted from eMMC then u-boot overrides
bootcmd to call emmc_boot.
Maybe it will be easier if I describe what I want to achieve:
For non production I would like to be able to:
- boot from either SD or eMMC (depending on boot dev detected by TF-A)
- boot from pxe / pxe network
- boot using boot script
- support A/B slots for kernel and rootfs
For production I would like to:
- restrict boot device only to eMMC
- support A/B slots for kernel and rootfs
- boot via signed and validated boot script (validated through
escb_validate command that's used to validate signed kernel, signed
scripts and so on).

That's being said, and given the following statement from U-BOOT's
docs: "If you are using custom boot scripts for your board, consider
creating your own bootmeth to hold the logic" I'm thinking about
creating my own boot method that would:
- check boot dev
- check if there is a boot script (and optionally validate it if
secure boot is enabled)
- select A/B slots for boot
- boot the system using boot script and FIT image
But I'm not sure if this makes sense and whether or not it's the right
/ modern way to boot OS on today's u-boot.
The other thing I'm wondering is - taking all the above requirements -
 how to integrate bootcounter and bootlimit in the overall solution?
Should I use altbootcmd or handle bootcounter liimit and A/B selection
in the boot script, or perhaps integrate everything in my custom
bootmethod?

I would be grateful if someone could point me in the right direction
regarding modern U-Boot practices for this type of setup.

Best regards
// Patryk