If you use polygrouping correctly, it works just fine. You can autogroup by angle and it does a really good job of capturing surfaces. When you Zremesh, you need to check options for grouping/borders. It works, try it sometime…
As for what I was saying earlier about the dynameshing workflow, to consolidate everything into one single mesh with all internals gone, you’d only want to do that if the object is to remain stationary. If you need things to move around, then you’re best off with just using what you’ve already got and might want to run decimation master to reduce poly counts if they are too high. DM works extremely well on hard surface geometry.