We play an average of 50 odd games a season. As Wenger has shown everyone so successfully in the recent past, relying on young players to play too many games results in them burning out. The worst thing we could do with our young trio is put them in a position where they're unchallenged as first choice in the squad.
Young players are also less able to handle the pressure of the expectations of a major club on their shoulders when they're out of form and not performing - look at Sterling's last season at Liverpool with Suarez gone and Sturridget injured, he saw his arse and decided to move somewhere where he had more chances of trophies and team-mates he could rely upon.
It's also a fact in football that players get injuries and suspensions, something our players suffer from more than most and as much as anyone.
He wouldn't be staying to be a 'row' player, he'd be staying to be a vital part of the first team squad, in fact even having 4 players capable of playing in those 3 positions wouldn't be enough, so we'd be on the lookout for another.
If you look at the problems our squad is suffering from at the moment, which is a sharp drop off in performance levels when the first choice players are unable to play, it's absolute stupidity to look at getting rid of Aguero without getting a replacement of a similar level (which doesn't solve your 'row' player issue in the slightest).
Also and this is something Aguero will be more than aware of, while he may have been guaranteed a first team spot here over the preceding 2 seasons when fully fit (due to us being far too thin on strikers in the squad), he won't find another club in Europe where this would be the case without taking a serious step down. Bayern have Lewandowski, Madrid Benzema, Bale and Ronaldo along with Morata, Juventus Dybala, HIguain and Mandzukic, PSG have Cavani, Barca have Neymar, Messi and Suarez, Chelsea have Costa, Monaco Falcao, Atleti have Griezmann and Dortmund have Aubemayang. So unless he wants to join a team with no serious ambitions to challenge for a top domestic league and the Champions League, he'd have to accept that he wasn't necessarily going to play every game regardless of form.
Plus, he's happy in Manchester and knows the club, we treat him well, pay him well and he knows that more than likely when his contract is up we'll allow him to go back to Independiente on a free, we won't stand in his way. Any other club that sign him now will be looking for a long term contract to absorb the cost of his transfer fee into their books and they'll want a fee to allow him to go back to Argentina before the end of that contract. He'd be silly to move and I think he knows that.
So unless Guardiola actually has no interest in keeping him here, which I don't believe for a second, Aguero staying here is not only the best option for us, it's the best option for him.
Very convincing argument, you should email that to Pep and Sergio. :)