Hello Stéphane,
I actually think it makes a lot of sense to allow non-contentious TLDs a way forward before the mainstream new TLD launch, if it means TLDs that present more complicated issues get ironed out properly while at the same time not delaying the others.
The problem becomes in defining "non-contentious TLDs". Even IDN-ccTLDs have issues around their contributions to costs and their commitment to adhere to IDNA standards. Every TLD applicant that I have come across claims that their TLD is "non-contentious". ICANN's experience with trying to manage a specific category (Sponsored in 2004) was not successful. By setting up one group to go forward early - you just increase the commercial incentives around trying to show that your application is in that category. The new gTLD process itself already has three categories - geographic, community, and other. Regards, Bruce