Hi,
Thanks for the posting. This is actually an interesting case. I searched the doc, it seems ,the official doc does not explicitly claim the limit for the KPIs in Tabular. From what I saw, I haven't heard there is limitation for this.
I think to create duplicated KPI for Alias use is a good work around for you situation, and should not impact you tabular model, in my opinion.
Regards,
Lukas