From the customer’s perspective:
– The software warranty should be for the duration of the subscription term. If it is a hybrid cloud model, the warranty should be valid for enough time for you to take the application through its paces in a live environment
– The supplier’s obligation to fix or replace the software should be at no extra cost to the customer. Given the criticality of the defects, you may also want to set out the time-limit within which you expect a fix.
– A termination right should be at the customer’s discretion. Along with the termination right, the supplier should provide the customer, at the very least, a refund. Liquidated damages may work, but can be tricky to enforce if not estimated correctly.
– These remedies should be in addition to all other remedies available under the law.
Look at all these factors holistically in the context of the warranty itself and the contract as a whole. As they say – in a contract, no clause is an island…