Customizing top menu for multisite

Hi – I am using this theme for a multisite project.

I am using a primary domain as well as several subfolders, with the primary domain and each subfolder having its own WordPress install.

From the user’s standpoint, the collection of websites should all appear to be part of the same website. So for example, myexcellentwebsite.com, myexcellentwebsite.com/alpha, myexcellentwebsite.com/beta, myexcellentwebsite.com/gamma, etc. are each using Mesocolumn, with each of those subfolders all being different websites with their own WordPress installs, but the user should not know the difference.

I would like to change the top menu to suit this purpose, in two ways:

1. I would like to change the “Home” button located in the top-left corner so that all of them lead to the primary domain. For example, clicking on the “Home” button on the subfolder websites myexcellentwebsite.com/alpha, myexcellentwebsite.com/beta, myexcellentwebsite.com/gamma, etc. would all take the user to the primary myexcellentwebsite.com. (They should still be able to get to the home page of the subfolder by clicking on the website title, which won’t be the same for every subfolder.)

2. I would like to include menu items that allow users to go between subfolders, not just to other pages within the same subfolder. Again, from the user’s standpoint, this is supposed to look like just one website, even though it isn’t.

Any ideas are appreciated. Thanks very much, I hope that wasn’t confusing.