Remove all themes for upgrade?

All of my themes in Ghost 1 are not compatible with Ghost 2. Even the default Casper theme.

In order to upgrade to Ghost 2 should I switch to the default Casper theme knowing that the Casper theme on the new version of Ghost will be compatible?

I don’t believe there is a way to remove all themes before upgrading to remove the possibility of problems?

When I upgrade will it automatically remove the themes?

I am thinking that the easiest way of getting Ghost 2 is to not migrate to it as this is not really possible unless you are a developer who knows how to do a whole lot of editing and changing of code? The best way is to do a clean install and then just redo all of your posts? Could be problematic if you have a lot of posts on your blog.

When I have been on some websites selling Ghost themes I am not noticing a lot of ones that are compatible with Ghost 2 or there is just no info on whether they are which leads me to believe they are not.

Perhaps I am just looking in the wrong places but there seems to be a lack of Ghost 2 themes available. Can anyone point me in the right direction for finding them?

I think I may, unfortunately, have to do a clean install of Ghost 2 and to wipe the blog I have at the moment due to the problems I’ve had trying to upgrade.

Update: It looks like it won’t allow me to change to the “default” Casper theme even within the Ghost 1.25.6 version I was rolled back to because it is not compatible and comes up with errors.

This means I might as well just delete the whole blog and do a clean install of version 2 and start over from scratch because it is simply not possible to upgrade and reimport your blog.