issues with command and custom_command

Trying to work around bug #1708066 (wrong TERM), I started using command= in my startup profile, which worked, except that

1- command= doesn't work for the default profile, and gets replaced by my shell

2- custom_command= with use_custom_command=true does work for the default profile, but then it overrides all the commands on all profiles, and cannot be disabled or overridden by setting either setting in said profiles.

How am I supposed to have a non-trivial default command that doesn't override other commands?

NB: Using terminator 1.0 from NixOS