Want to take a stab at extending Sustain? Here are some ideas:

Challenge your colleague

For all the accepted challenges, enable employees to share it with colleagues. Sharing will send notification to the activity feed and which on click will redirect user to the challenge details

KPI and Metrics

Implement Power BI analytics to have deeper insights on impact

Credly integration

Integrate with Credly to credentialed employee achievements

Intelligence challenges

Create challenges that can be tracked and completed based on employee engagement rather based on honor system