StarWaves
If MC can get both Vali and Ingvild as allies/followers, it can be a moral blow to the devils' faction in her own Dxd universe, The original maous were seen for the other devils as deities. If MC turn them strong enough and present themself as legitimate heirs, they would can at least divide the devils, plus MC offering all reincarnated devil turn bacl previous species, devil faction would lose an important porion of their power and easier take care of remaining devils without turn in a genocide