With current Automation Studio possibility you can only use existing Widgets in MappView.
Have a look at this post from Andrej Kolmanic. Widget Development Kit
I think the WDTC is the way to go for HTML Developer, to create new Widgets.
There is also the possibility to use the Webserver of Automation Runtime instead of mappView. In this case you have to write the whole Visualisation in HTML.
Greetings
Michael