A version of complex vouchers were already done in response to the RFP #3. However, with the upcoming completion of the output unification, we will be able to implement the complex vouchers as a library, using DelegateCall, making it a lot easier to use and with more functionalities.
Guilherme did a nice write up about examples of useful comple vouchers in this Github issue.
Time based vouchers also have a bunch of applications in finance. For example, we could have a forward operation that allows me to buy X amount of a token in a future date for a certain price x. The application can generate two vouchers at the moment of the deal that can only be executed at the forward contract expiration date: one transfer of x eth from the buyer to the seller and a transfer of X tokens to the buyer.