That could be the way to go. I assume you have scaffolding in place. If the cladding is removed could you build an internal temporary support whilst standing on the scaffolding. Building it from the inside would be difficult, depending on your age and mobility. Presumably it is just a case of internal temporary supports to replacing the vertical timber members at the front.It's possible that I could just build another frontage, just behind the rotten one to support the dormer gable, from inside the loft and then remove the rotten beam and replace the whole thing.
Timber cladding in that location is always going to be a maintenance liability. Personally I would either replace it with something else which does not rot or if that is not acceptable for aesthetic reasons, then have a weatherproof facade made of non rotting material with the timber cladding as an easily removable/replace decoration, with ventilation as you intend.
On my recent new build, I have dormers and went for lead cladding. It suited the property, accommodates any movement and is low maintenance. Expensive to buy but cheap to install. Tile alternative would have required very expensive external corner tiles. Timber cladding was ruled out, looking to the future I need low maintenance.