Integrate a younger qt version in an older yocto release

Our project is based on the meanwhile outdated yocto *warrior*, which was first modified by the vendor of our SoM. Then we integrated the FreeScale/NXP kernel into it because the mainline kernel did not support GPU functionality we needed. It has been quite a ride to get this working, but now there is need to switch from qt 5.12 as included in our *warrior* to qt 5.15 (LTS). We want to avoid switching to a new yocto release, but only changing the checkout of the meta-qt5 layer leads to bitbake problems like ERROR: ParseError at meta-qt5/recipes-qt/qt5/qtwebengine_git.bb:83: Could not inherit file classes/features_check.bbclass and I expect this to be only the first of a series of incompatibilities, so I'm asking myself what would be the best approach to the problem. Should I start my own meta-qt5 branch, changing the recipes to use qt 5.15.8 and only cherry-pick commits from current meta-qt5 branches?