I’ve considered this, but what would you do about the problem with overcrowded maps as a result? If you have to grind, needless to say you’re going to have to stay on the same map for a long time.
Solution #1: Add new sub-areas that branch off the main fields, eg. Legwyn Residence - B2F, Forest of Prayer - Path of Devotion, Tenet Garden - Northwest, etc. This is extremely doable if you notice the number of areas that have paths that don’t go anywhere. Just build superpowered monsters (20 to 30 levels higher?) adventurers can backtrack to later.
Solution #2: Increase the number of channels. This is a bad idea because increasing the number of channels is tantamount to increasing the spawn limit for monsters. If you limit the channels you can control the rarity of items easier. For example, 20 channels in Crystal Mines 3F makes Vubbe Fighter Blood quite less rare than Bloodstones from Goddess’ Ancient Garden.
Solution #3: Increase the cap on Missions/Dungeons. This would make instance based gameplay more of a focus, which I’ve heard a lot of squawking about on the forums. “This isn’t Tera! This isn’t FFXIV!” etc. But it’s not an impossible option, and would be safer than trying to control the number of channels and cheaper than designing a new map.
Solution #4: It may not be obvious but keeping the cards the way they are is another choice. Just decrease the amount of EXP they give by a substantial amount to provoke grinding more would be fine. However, we’ve seen the results of this from CBT1. Players started dropping out of the game at around LV40. Though the general explanation for this was IMC and the Translators needed to limit the areas that haven’t been translated/worked on, the results are still there as clear as day for people to examine.