I'm really not one for this "training with champions" and "learn from senior player" stuff that people like to talk up.
Some act as if having young players training alongside great older players is like giving them steroids. Not saying there's zero benefit in it, but IMO nothing beats actually playing consistently.
If Radu isn't going to be playing for the next 6 months, bring the boy home then. Better he train here than in that trainwreck of a club.
Well, truth is that the bext experience is to be playing with champions, not just training with them. But we've tried that with Sebastian Frey and the results were disastrous. A young goalkeeper is best served training with the best. He trains with them 5/6 times a week while a game is less than 2 hours work. If your training sessions aren't up to standards, those 2 hours of official games won't really do you much good aside from learning to cope with pressure. It can also be a devastating factor for a gk who relies on confidence. If your team and defence sucks it's not a really good 'school' for you. At least for more than a season.
With that being said, Radu is best off sent to a top team in a mid-tier league. The same formula I suggest for most of our non-Italian prospects. Send them to Holland, Greece, Belgium, Portugal, Russia, Turkey, Sweden, Serbia or wherever there's championship pressure and a demand by the fanbase to win all games (yes, fans can be irrational like that) and also get to play in UEFA competitions being a minnow in most of the games. Usually there are 2-4 teams in those leagus that will compete for the championship so that gives you a pool of like 30 teams you can opt to send someone for a proper football experience. This is also the mindset of players you need to have.
Italians on the other hand do not have this luxury as not everyone can belong to the big three [historically] and top talent develops everywhere*. It's just up to the player to make the right move and the right time. Otherwise you end up being like Stefano Fiore who was unlucky to make all the wrong choices (left Parma slightly early for an Udinese team that took off some years after the fact, then moved to Lazio when they started deteriorating and it was game over for him). Barella on the other hand made the move at the right time and I'm very excited to have him around.
Sending them just to get playing time is a way of telling them "you're never going to play here".
As for Radu, if he's sent back, I'd rather keep him around if he's mentally capable of handling it. Loaning him to another Serie A club would be the ideal situation as he's got used to being a Serie A starter and you avoid having him feeling terrible for going to 1st choice somewhere to 3rd choice at Inter. But it won't be the desired result in terms of his development to make the move.
* And this is exactly what ruined the previous generation, Juventus' trying to pull this off by themselves and monopolizing the Italian market, owning 3/4 of all Italian prospects and then just scattering them around for on the pitch or off the pitch benefits.