Backportability of bird2 debian package

Hi, I have a request to Ondřej Surý: debian-packaged version of bird2 that is currently on https://salsa.debian.org/debian/bird2.git is unbuildable on older distros because of required version of debhelper (cosmic and stretch have version 11) and init-system-helpers (cosmic has 1.54, stretch - 1.48). Could these dependencies be relaxed to ease backporting of the package? Thanks, Eugene