WCS becomes backup PF next to backup center JT (actually PF defensively and C/PF to JT's PF/C offensively) and 4th big, logging 10-12 minutes plus all the garbage time to start the season, and likely capable to give Kings up to 30 productive minutes every game by January 2016.
PF should be occupied basically by JT with better perimeter play on both ends.
Kings need to find either a combo-guard, who would assume backup SG role next to Miller, but would also be capable of logging many more minutes at both guard positions in case of an injury (Stuckey looks perfect for this role and is very much available, if Kings act swiftly like with Collison last summer; Cory Joseph might be able to do that as well, but when Spurs had shallow guard depth last season, he was pretty underwhelming), or look for both backup PG and SG with Dre returning simply for depth purposes, but both those guys should be capable of spot starter duty, and I'm not sure, Kings have resources to pull that off.
Williams, Mccallum and Stauskas were worse Kings defenders by a margin (at least team defense crumbled with any of them on the court), while Landry in the post absolutely killed offense as he got in the way of both scoring options, especially Rudy. Williams should be gone, and Kings can't afford having the other two in 10-man rotation. Carl was shooting pretty good from mid-range last season, so if he's still on the team come training camp, Landry can be used as an emergency big, stationed in high post to spread the floor, when not involved in screening.
P.S. Kings have very limited resources both in terms of assets and salaries, they can absorb with cap space or sent out and consequently taken back, so Ben is not going anywhere from the starting lineup - he's a good low-cost, low-usage SG on a team with two hungry scoring options and PG capable of scoring.