I agree totally Andy. Of course, if player is looked at individually, I have no doubt Lucho Gonzalez will make best investment. Lucho is absolute monster, and he is only going to get better with age.
But what if Marchiso and Paro, are better prospect than we initially expected? Then we might have spent needless youth premium on Lucho when we already had good replacement down in our own farm. Its simply a waste from financial perspectives, and teams operate with returns in their mind not just sporting concern.
I like the CV of Marchiso. He was a captain of all conquering youth academy which had Domenico Cristico in the squad. Its shows boy has some leadership skills, mental aptitude, and class. He sounds like somebody we should definitely have a look before just discarding away. A year loan with teams like Siena won't be so bad IMO, then recall him if Gilberto shows sign of decline.
Just as importantly, Gilberto is a player I am certain the top professional players will recognize and respect. He has played against like of Del Piero, Buffon, and Camo, so our players know what they are getting. This may persuade them to stay.
Now the real question is why would he want to leave Arsenal as Juventus710 asked? Apart from money, and playing for more prestigious club I see no reason. He seems settled in UK, and going pretty well in both EPL and Europe with Arsenal. Its not a profile of player looking for a move.