I was in discussions with a potential spouse and it hit a stumbling block as she asked me to consider changing how I pray my namaz and include Aliun Waliullah. Is this forbidden and is there any Hadith from our Imams a.s to illustrate this?

We cannot add or subtract anything from the wajibaat on our own accord.
If one is a mujtahid, then they can analyse Quran and Hadith regarding this issue, and if one is a muqallid (follower) then they must follow what their mujtahid has ruled on this issue, just like everything else.