I doubt that it will happen, but even if there`s a small possibility, then Marcelo is a no-brainer. He is literally THE left back of the last decade, he`s got worldwide reputation and recognition, he is an obvious upgrade on Alex Sandro, just like Ronaldo was for Higuain. That doesnt mean that Sandro and Higuain are bad players, on the contrary - they are very good players, but when compared to the absolute best on their positions like Marcelo and Ronaldo, its obvious that they are inferior, thats not debatable.
Age is irrelevant here, he`s got it all, he was top class at 25, is top class at 30 and will still be even at 34/35. Money is another factor that doesnt really matter - top players cost more money and earn the most, if you want the best left back in football you have to pay him accordingly.
A big yes to Marcelo, if the board is confident that we can afford him, then go ahead and sign him!