I see no problem with modifying ROPS as long as it's done well. It is always at your own risk. Suggest OP improves his design.
Agree with others that the link is a weak point in compression (flipping over backwards) or from lateral forces in a side roll. At a minimum I'd add a second link to the other side of the tab. However I'd rather see square tubing of the same thickness. Tubing will better handle forces from all directions. However, just angling the upper ROPS will change forces on the lower ROPS. Without re-engineering the entire ROPS, there will always be risks to simple changes that impact the rest of the system.
My ROPS are cut, lowered and angled. But it was done as part of a larger system that far exceeds the function of the original ROPS for any senario I can think of.