Hypothesis for an engineering project that can't be tested due to time constraints
For your specific case:

You could create a basic version of the system in a short time and conduct a study with a small number of clinicians. Have one group of them use it, and one group not use it. Define metrics that capture user variables (ease of use, tangible benefits) and system variables (how much different features are used, how much it adds to any existing discussion on products etc.). Make small changes in the system to change these variables, and map the outputs. By doing this, you already have an alpha-test, which will help you pitch the system when it is actually developed.

For the general case:

Often it is not possible to test the actual system/design/product in a limited time-frame. A good solution is to identify different parts of the system/design/product, compare these with existing systems and isolate parts that are unique and/or critical improvements. Develop just these parts, and test them either physically or through some kind of simulation. If it is a simulation, do some validation testing to increase confidence. Document everything, and generate sensible statistics during testing. Honestly report all the positive outcomes, the flaws and methods to tackle the flaws.