It has been said in the past by the release team that the current autobuilder behaviour of only considering the first option for a build-dependency is by design to improve the determinism of the autobuilding process. I don't think you will persuade them to change it.
The proper fix IMO would be to add support for version ranges to dependencies in dpkg, but even if you can get the dpkg developers to agree to do that it would not be a quick solution as any change to dependency metadata takes a long time to trickle down to the many tools used in Debian.
