What's your proposal? Because taking an approach that isn't data driven means it needs to be a replacement, and you need to convince people that it's worth the risk of nepotism and bias.
Nepotism and bias aren't the alternative here. If you require that decisions are driven by data and you don't have access to accurate data, you should default to doing nothing. If anything, nepotism and bias sneak in when decisions are made despite the fact that no accurate data is avaliable.