In principle although a ticket can be open dated you do have to decide the routing, and routing includes whether you will transit or stopover between each segment.

In practice I tend just to go for stopover everywhere except in the continent of origin where I have to specify the two stopvers. I know this might be costing me a little nmore than necessary, but frankly I am not that price sensitive.

My expectation is that a change from X to O (i.e. transit to stopover) would be a ticket reissue (because the tax has to be recalculated) and hence a $75 fee.