I worry constantly just packing around a rifle with a long range tang sight. Moving through any kind of impediments with a front sight hanging out there looks like an invitation for trouble. Probably fine for a bench or stand hunting unit, but I'd not take one through the timber.
The MVA Globe Front Sights are pretty rugged and the #111 is sans the Spirit Level.
I'm not sure if they still have it or not but Shiloh once offered a similar sight that has a post and globe permanently mounted in it. It looked like a VERY rugged Front Sight.
As for the delicate Target style Tang Mounted Rear Sights, you're right they are fragile.
On my Big 50 I've left on the original sights, front and rear and added one of the earlier style Sharps "Sporting" rear mounted tang sights. That sight looks like this.
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It doesn't have nearly the fine adjustment on it, but it does give you a good long range sight picture and longer sight radius.
It's a fairly tough sight and could take a bit of abuse without getting too beaten up.
Of course if you're in timber so thick that you have to worry about sight damage, you're probably not going to need a long range sight!