Hi there! I am also trying to notify team members of a deal lost/won!
We can do it through “send internal email notification”, but as discussed above, in this case it is not possible to include other objects personalization tokens.
For us it would also be interesting to be able to personalize the email template, so I would suggest including the same feature available in Contacts workflows: “send internal marketing email”. This way, we can use all properties available in other objects and personalize the template accordingly, also selecting who the e-mail should be sent to.