The way themes are built has completely changed between Totara 1.1 and 2.2, so your theme would need to be rewritten anyway to work in 2.2 at all.

If you're planning on upgrading to 2.2 soon I'd suggest waiting until you're on 2.2 before making the changes. You might find that the customisable theme is suitable for your needs and if not it will be easier to customise via additional css.

Simon