On premise server migration - Repointing of data source

have you tried to use TMDL view (preview feature in power bi desktop)?

you can script the entire model (all the tables) at once and with a Find and Replace substitue all the occurences of your old db with the new one and then publish.

https://learn.microsoft.com/it-it/power-bi/transform-model/desktop-tmdl-view

if you leverage Power BI Project you can even do it for all the reports at once.

https://learn.microsoft.com/it-it/power-bi/developer/projects/projects-dataset

anyway the parameters suggestion it's worth to be implemented asap.