Random thought, maybe unpopular-- I've been seeing a lot of people talk about putting Joshua on that Sherwood line when he gets back, and personally, I would try just about everything else before I try that. That Blueger line has been killing it, Heinen has actually been an underrated piece of it (while looking invisible on other lines), and you now have the opportunity/luxury to have three, maybe even four fully dominant/reliable/tireless lines by using Joshua somewhere else.
He could bring stability to the Miller line in a way that DeBrusk isn't currently, he could rekindle his magic with Garland and potentially really help Pettersson, or he could massively upgrade the Bains spot and bring stability to Sprong without losing any offense. He could even also potentially carry his own second line with Garland (like last season) to free up a Lotto line without turning them into a one-line team.
There are a ton of better options than laterally replacing Heinen with Joshua, IMO.
Last season, we kept thinking "wouldn't it be great if we could just clone Joshua/Garland and put them on each line?"-- Now we have an opportunity to have something to that effect and we're not going to do that?