Nope you're not tired.
Templated constructor functions are not currently supported in D. :(
Ouch.
I did that many many times, but for structs. Case in point, I encountered this while deciding to switch from struct to classes, thinking inheritance would suppress lot of code duplication. Aw, man, first time in months I use classes in D, and it's killed in the womb.
OK, there are solutions for for what I envision, but that will be more painful.