Times change, I highly doubt a modern motherboard will give in due to a heavy cooler. Only risk of that is if the system is being moved around a lot which I doubt is the case here. Also an AIO isn't going to be quiet as an air cooler either which might be a priority if a lot of rendering is going to be carried out. So I don't see much reason to go with an AIO solution in this scenario and most workstation builds are air cooled anyway
For a workstation, I think a proper water cooling loop is the way to go if you're looking down that route.
