Email & Data Capture for Multisite

Two thing I offer:

1. Tutorials:
If it were me, I would build my own plugin using a tutorial (adding only what I need and no cruft):

For example,
http://justintadlock.com/archives/2009/09/10/adding-and-using-custom-user-profile-fields

and

http://www.cozmoslabs.com/1012-wordpress-user-registration-template-and-custom-user-profile-fields/

Lots to read (in the comments), but it should produce an enhanced profile page that is indeed Network savvy and only what you want.

2. Plugins:
There is multisite support for Cimy User Extra Fields:
https://wordpress.org/plugins/cimy-user-extra-fields/installation/

http://wordpress.org/plugins/profile-builder/
(pro version upgrades to the extra fields it appears.)