The obvious answer is that nobody's going to fill those particular roles. Walker will provide more scoring than Gabby, less defense and passing, a lot of rebounding. It's quite possible that the work she did with Collier last summer will lead to a connection between them and a lot of passes between them in the high/low post. ONO can provide the back-line shot blocking. I'm hoping that some combination of Williams and Coombs can provide some perimeter defense in Kia's absence. If Camara is healthy, she can provide a bruiser inside, something we haven't had in a few years.
WRT EricLA's post, cutting back the minutes of 5-6 players doesn't have to mean having all the scrubs out there at once. You can cut five players back from 36 to 30 minutes a game by playing two people for 15 minutes, etc. I'm thinking the bench is deep with good players. In addition to the returning starters plus Walker, we'll possibly get quality minutes from Camara, Coombs, Williams, Nelson-Odota, and Irwin. I'm hopeful that Gordon will make a significant sophomore leap. I'd love to see Molly make a junior leap, but I'm just not sure it's in the cards.
One great thing about this team is they can go with different looks. Most obviously big (ONO, Collier, Walker, Samuelson, and Dangerfield) and small (Collier, Samuelson, Williams, Coombs, and Danger). They have amazing scoring potential, and if they can develop the team defense of two years ago by the end of the season, they'll be a lot of fun to watch.