What are the possibilities to brand (change style, fonts and logo's and for SharePoint masterpage) the Office 365 environment and what are the reconmendations? In my point of view there are some parts which can not be branded (Mail, Calendar and Contacts).
Other parts can be branded (The SharePoint sites). But some parts of SharePoint will be difficult to brand. For example I think it will be very difficult to apply a custom masterpage for the MySite. Or am I wrong?
I would not look to brand the Mysite page myself as it would end badly.
I think developing something which still has the blue bar at the top and then whatever company branding you have as a part of the SharePoint site would work best.
The easiest way to provision this still is unfortunately through a Sandbox site as SharePoint apps do not have "local" event recievers so if you wanted to apply the branding to sub-sites when they are created it is a bit difficult to do using a SharePoint
app (likely involving visiting the app again).
There are a few things you would need to change with this:
Instead of v4.master copy seattle.master using SharePoint designer
Use a UI version of 5
Sandbox solutions do have a disadvantage that they need a local SharePoint farm with visual studio unfortunately. I am looking at creating something that will do this using a remote event receiver however this would mean you would have to host it as
an auto-hosted app for each site collection or host the code for it yourself somewhere - not ideal.