Sure, you could do that. Ubuntu is Free Software, and you have root and the source code on the phone, and presumably will have the same on the tablet. So you can customise it at your will, including automation, if you're prepared to put in that effort.
Isn't there a nice way to have it both ways, i.e. automate all changes in a script, and roll it after each image update? Assuming most things that may need to be hacked away don't see breaking changes after each update?