@derweili – That is not something we control, so if its possible with WP, its should be possible with our plugin. To be clear we call get_the_excerpt to generate excerpts by default, so that’s effecitvely where you should be looking to make the needed changes.
That said we are releasing a Pro version and some cool addons including Content Teasers such as those on NYT or Wall Street Journal. Its gonna be available next week. That solution does include a custom teaser generator that fully maintains all formatting and html structures, and can truncate chars, words, sentences or block level elements (paragraphs, divs, img etc).
You can try a demo of the early version here: https://app.instawp.io/launch?t=content-control-pro-demo—star-wars-theme&d=v2
