While this is a good suggestion, the availability of TSC II is not that scarce with the recent addition of fantasy dungeons. From my understanding, TSC II drop often from the main bosses (2 in 80F/ 3 in 110F). There is also the "Timed dungeon" feature that gives 1 TSC II a day for completing it. Although TSC II aren't as abundant as many would like, it is available in decent amounts.
Obviously if you are not strong enough for the fantasy dungeons, it is a problem. That being said your idea is great for those who are unable to complete the fantasy dungeons. However with the plethora of TSC I in game right now it would just make the game unbalanced for those who don't have TSC I. I myself have almost 400 TSC I versus someone else who is newer only has 5-10 TSC I laying around. There may also be people who have 1,000 TSC I.
As for the idea of making TSC I able to sell, if you mean being able to sell it for copper, that is a good idea. However, making TSC I unbound and able to be sold in the auction house, that concept was removed for various reasons before.