I have to say, a challenge system (with referee’s calls for ambiguous situations) does create an additional strategic quality. But there’s no point in using a challenge system if you’re also going to deliberately compromise the ability of VAR to reach the right outcome. You’d just end up with a whole bunch of complaints along the lines of “it’s absurd and unfair that we’re getting relegated instead of them because the ref couldn’t spend long enough checking every possible offside and consequently they get to have an offside goal”.