Seconded! In the current world where dashboards are coupled to alerts, it's very frustrating not to be able to define alerts on a templated dashboard.

It's also frustrating that it's effectively impossible with the Cloudwatch data source to select resources to alert on using their tags (e.g. select the elb with app=foo and env=prod). The dimension_values() function lets you filter based on tags, but instead of being usable directly in a panel's query it requires using a variable as an intermediary, which then disables alerting.