as suggested by @adrianschroeter https://github.com/openSUSE/kiwi/pull/541 should be solved on OBS level. The problem are kiwi VMX builds for SLE that need kernel-default-base instead of kernel-default. Both packages conflict with each other. The special kiwi-desc-vmxboot-requires package however requires kernel-default, so when the kiwi file specifies kernel-default-base OBS throws a package conflict even though the kernel packages are just meant to be put in the repo used by kiwi, they are not required to set up the build environment. So the conflict actually doesn't matter. Therefore OBS should ignore conflicts between packages that are just input for kiwi.
as suggested by @adrianschroeter https://github.com/openSUSE/kiwi/pull/541 should be solved on OBS level. The problem are kiwi VMX builds for SLE that need kernel-default-base instead of kernel-default. Both packages conflict with each other. The special kiwi-desc-vmxboot-requires package however requires kernel-default, so when the kiwi file specifies kernel-default-base OBS throws a package conflict even though the kernel packages are just meant to be put in the repo used by kiwi, they are not required to set up the build environment. So the conflict actually doesn't matter. Therefore OBS should ignore conflicts between packages that are just input for kiwi.