I ended up getting the Marine and had it changed to a blue rubber strap at a Breguet/Swatch service center.
Although I never ended up changing the strap on this particular watch, I did also get a Breguet Tradition 7027 relatively recently and I removed the screwed bars myself so I can use quick change straps with it instead. You would need a precisely fitting pair of two screwdrivers, one to hold one end and the other to unscrew. And something to hold the watch in place. I dont recall the size on the 7027 (and it may be different to the marine in any case). I bought two sets of watch makers screwdrivers with multiple sizes and just found the pair with the most snug fit in the screw head.
All in all not too difficult but care must be taken not to slip and scratch the watch. And the exact fit is important so as not to damage the screw head. Its entirely doable yourself but a bit of a hassle if you want to change straps regularly.