I think his choice of shadow cabinet should give a good early indicator of the direction he might take Labour in. Though if he does go for a compromise route and loses the next election that'll basically guarantee that the next leader will be a full-on Blairite.
Rosena Allin-Khan seems like an obvious choice for Health Sec right now, don't know much about her positions but having an actual NHS doctor in the shadow cabinet, especially in the current crisis opposite Matt Hancock of all people, may be beneficial. Just please don't give Jess Phillips a position.
EDIT: some positions coming out now
Shadow Chancellor - Anneliese Dodds
Foreign Secretary - Lisa Nandy
Home Secretary - Nick Thomas-Symonds
Cabinet Office - Rachel Reeves
Health Secretary - Jon Ashworth