Could victory buy the Qing a controlled transition?

Could Qing victories in Tonkin and Korea prevent the dynasty's collapse?

Probably not, but they might give the regime enough strength to manage a constitutional or otherwise controlled transition.

Military success alone would not resolve the Qing dynasty's deep internal institutional problems. Victories in Tonkin and Korea might still provide enough legitimacy and time for a controlled transfer of power, perhaps toward constitutional monarchy. That could replace a violent, fragmented collapse with a managed transition. The counterfactual changes the form and pace of political change more plausibly than it prevents change altogether.