Hello,
maybe I understood it wrong, but does it helps, when you load bootstrap css before ionic?
Maybe a try worth. Looking to variables.sccs there is a import from ionic.globals. Maybe it helps, when you try importing bootstrp.css before them.
If this not helps, then you can maybe take a look to the ionic css file, that are in
node_modules\ionic-angular\themes and node_modules\ionic-angular\css, but these files are not a limmerick.
Best regards, anna-liebt