I can't see your photo's with my phone...
Exhaust studs can be a nightmare though. Whatever you decide to do, i would suggest regularly spraying them with plusgas and/or some kind of rust treatment now.
When I bought my bike, mine sheared off with no effort whatsoever. Such little force that I hadn't even considered using heat or penetrator fluid first. :-(
If they shear off short or flush with the engine, their location makes them a pig to drill out... Then if you snap an easy-out in the hole
you're proper screwed and it's a new head job.
If it ain't broke... perhaps it's a job for winter. ;-P