You maybe could just copy whichever door you wanna use in blocks.xml, and use the ModelOffset property to center it in its block space. It might be a bit wonky when trying to interact with the part of the door that would then extend outside its space when opened, but I'd think it wouldn't be too bad. Something like
<property name="ModelOffset" value="0,0,-0.5"/>
might be what you want. Not tested though, so the value needed will likely be different. But that should get you on your way.