If the Bruins were allowed contract extension numbers, I think he'd be a big void filler both short term and long term. Replacing one Czech with another.
With the goal of Hertl re-signing, I'd offer:
One of Studnicka, Frederic, Beecher (top C prospect, and 2 previous firsts)
One of Zboril, Vaakanen (both 1st round draft picks, Zboril is more ready, but I think Vaak has higher upside)
1st 2022
Conditional 1st 2023 (as long as the Bruins make the playoffs in 2023)
And probably need to add salary there somewhere.