Context - I used to work in Finance at LFC, during FSG's tenure.
Ethical concerns:
Perhaps "ethical" isn't quite the right word. I trust FSG to act in a mostly ethical manner and I wouldn't have concerns about them exploiting MCO in an underhand manner. However, as football fans, we have a strong connection to our clubs and to their identity. The connection with Liverpool has weakened a lot for most fans over the past few decades as football has become less about community and more about business. This isn't necessarily an FSG thing, it's happening across the game, but it's probably more obvious at Liverpool. As the club has a global following and a huge reach, there are large numbers of fans who would like to interact with the players in particular and that's just not possible, but it means everyone gets shut out, and the team we support starts to feel more and more distant from us as fans, particularly as it's so hard to get tickets. This was as true as a senior staff member as it was as a fan - during my time at the club I had very little contact with the players and manager.
My concern would be that Getafe fans will see a similar distance put between them and their players / manager, where perhaps that isn't quite the case right now. But more than that, they would almost certainly be an unequal partner in a relationship between the two clubs, and I would worry that their fanbase would see their closeness to their club undermined. For example, and this is something we've talked about on this site in the past, Liverpool will often ear-mark a player as a target for the first team, but often they are not ready to go straight into our team. At present, we tend to allow that player to develop at their current club and then pay a higher fee later on for a finished article. One of the benefits of the MCO model would be to sign that player at a lower price in the sub-ordinate club (Getafe), allow them to develop and then transfer them to the dominant club (Liverpool). This is most clearly seen at the Red Bull clubs, where players often sign from Africa or Eastern Europe to the Salzburg club and then graduate to Leipzig if they show promise. If I were a Getafe fan, I'd be concerned that my club would be used in the same way, and also that they would be forced to take players from Liverpool who need more first-team experience.
In short, MCO works well for the dominant club, but there is a risk of significant dysfunctional behaviour at the subordinate club.
Does it fit with Liverpool's identity?
In short, it fits with our current identity, and I wish it didn't. I would like us to be less "corporate" but in order to succeed in the current iteration of professional football, we need to be corporate.
From a simple management perspective, MCO would give Liverpool plenty of opportunities to play the transfer market more efficiently, but only to the detriment of Getafe's individual identity.
Benefits to Liverpool
Ability to warehouse young talent and to buy in talent from markets such as Africa and South America where we might struggle to secure work permits for players. The classic example here is Leo Messi. Because of work permit restrictions, Liverpool could not have signed him when he moved to Barcelona, but it was obvious he was going to become one of the best players of his generation. The club could use the more flexible labour rules in Spain to sign such a player in future at a younger age.
That said, if we look at Manchester City, who have an MCO model, in recent years the players they have signed from affiliated clubs haven't always been successful (Aaron Mooy and Savinho are the only two I can remember) whilst they have also lost a lot of talented young players of their own to other clubs - i.e. it hasn't massively helped them to either recruit the best talent, nor to retain the best talent already on their books. What it has allowed them to do is to inflate profits / depress losses in their own UK operations (when they set up their MCO model they did a corporate restructure that shifted large amounts of cost of their books and into subsidiaries). I don't believe Liverpool need to do that, nor that they would from an ethical perspective.
