We are using O365/Sharepoint Online 2013 and I wanted to do some small CSS changes to MySites globally. I noticed that as the "SharePoint Server Publishing Infrastructure" feature in the MySite root settings is not enabled, I can't enter the alternate style sheet in the settings via the settings menu and if I try to use direct url "...-my.sharepoint.com/_layouts/15/ChangeSiteMasterPage.aspx" I get an error.
So my question has two parts. First is there a way to apply global CSS changes without activating the "SharePoint Server Publishing Infrastructure" feature in MySite root level?
Secondly, if there isn't, are there any downsides in enabling the "SharePoint Server Publishing Infrastructure" in MySite root level?