Well the rules of the Spacer start itself are set in code, so it's pretty hard for a user to add/modify a script to handle those things.
Console's AddCredits command takes negative values to reduce player credits (and won't go below a credit balance of zero), so you could just run that at start.
For capping relations, you could try creating a maxRelations table in data/config/exerelinFactionConfig/player.json like so:
"maxRelationships":{ "default":-0.76, "pirates":1, "independent":1 },
(Note that you can't set starting relationships in the same way, since that setting is only used in random sector, have to do it the old-fashioned way with console. Also this will affect other savegames.)
Thanks, this actually gets me close enough to the desired start without needing to fiddle too much with starting console commands. The only commands I needed to do with this setup is the one to drain my cash and set pirates to non-hostile.
The thing about the inability to set starting relations is that it actually snaps to their value limits once you use the SetRelations command on any faction, so by setting pirates to neutral, it automatically snapped the rest of the faction relations to -76, so getting started was surprisingly quick.