Brian,
I'm one of those people that has no idea what they will have in the yard to sequence to well into October so my strategy in XL4 last year was to create models as I needed them, all the big known stuff first and all the smaller ad-hoc stuff then just tacked on the end, often with shared absolute numbers whilst I sorted final layout.
creating the models allows you to sequence even if the preview is not 100% correct.
After I had finalised things I went back in and reconfigured all additional models added to used contiguous numbering, yes it's a bit of a pain but I personally think it's easier than leaving gaps.
It was only at this point I configured the FPP instances on the Pi's and BBB's and then spent the evening before go live configuring all the external controllers
