RMCS Modification scenarios

We have various RMCS Contract Modification scenarios and want to know the best way to deal with them.

1. Term change ( Start or end date) along with price change.
2. Term change without price change.
3. Price renegotiation without term change.
4. Addition of new products.
5. Change in Ship to, Bill To.
6. Tax Change resulting in Taxable value i.e. Revenue value change.
7. One time goodwill credit i.e. subsequent discounts.

Can you please let me know what's better - material/immaterial modifications or cancellation & recreation against each one of the above ?