I think you can design in error tolerance, with a bit of imagination. Imagine a flotilla of connected balloons, instead of one giant balloon; build in enough tolerance that a sagging balloon is supported by its neighbors until it can be fixed up.

Ultimately, it's a question of building a floating thing, and keeping it floating. This strikes me as not-too-hard, compared to the usual space problem of trying to hold oxygen in a bubble in a vacuum. You just need a sustainable way to 'recharge' the balloons; that really just means filtering lighter gasses from the air and pumping them in faster than they leak out. The Venus atmosphere is primarily CO2 with a bit of nitrogen; the game is then filtering out CO2 and filling the balloons with nitrogen. Coincidentally, we have people putting lots of thought into efficiently filtering CO2 from air already...