Model a first order system with input delay - Padé approximant?

Yes, e.g. in the cacsd module, but a help page is also needed (in the spirit of Padé approximation of models with time delay - MATLAB pade - MathWorks France). In the source of pade() you should control the type of input arguments by using the new mechanism (see When you have all these elements working in your fork you can create a merge request.