Defining a custom storage layout

Hi,

We're in the process of evaluating MAAS for provisioning our server estate, and one issue we've come across is we need to use a custom LVM layout (lvroot /, lvhome /home, lvvar /var etc.)

We've found that typing this in for every server deployment is both time consuming and error prone.
As we use the same standardised configuration across all our hosts (~2000) are we able to set a custom storage layout?

I don't see a straightforward way of doing this using either the default storage layouts or by modifying the curtin files, since the page below suggests using early or late commands, but we want to modify the partitioning config.
https://maas.io/docs/custom-machine-setup

Any help, or pointers in the right direction would be greatly appreciated.

Thanks,
Jak