Interesting conjecture, and I myself have thought on similar lines. Like, if I went back in time and placed a huge bet on a football match that I knew the outcome of. What would happen to the future that I had travelled back from?

My conclusion was parallel universes would be created, to accommodate my new actions.

However, these are, as you say, complete conjecture, because, unless you have a completely provable way of changing your past, there is no way of testing your theories, or indeed conjectures.

Nice thought patterns though... :-)

Cg