Barcelona 2009-2012, Real Madrid 2014-2018, Bayern, City, and now Liverpool have all seen success due to how reliant they are on their full backs. I would argue our system more so than them rely on our fullbacks the most.
There is a major risk Chilwell doesn't come back the same player. If Theo is available and wants to come, I say go all in as he can become an elite LWB. Not to mention as Vesper alluded to, he can play LCB as well.