I'm not sure really. Having trusts for more trials and other difficult content is a great idea, although not for ultimate. There should still be challenges you have to overcome with a group of people. Learning old ex and savage synced (and unreal for that matter) - I agree it's painful trying to find groups for that on quiet DCs. However they are quite good to do unsync and can be completed with various group sizes - sometimes there are still mechanics to think about to make it interesting too - so are trusts really necessary for that after all?

Perhaps the best solution would be to expand trusts to EX and savage, but only on low pop servers like Materia.