Weekly cap in Second Coil and loot in ST have their reasons to be there.

We all would like to be free and run content as we liked. But once accepted the limits, they have good sides: you have done your weekly Coil or got your loot from ST, you go and do other things. You have less pressure to repeat it endlessly it so that you get all your gear ASAP. The more time passes, the more things you have the possibility to do as new content is coming (beast tribes, crafting, PVP, hunting, etc.)

Of course we all would like to have new content quickly, not to have to do super long grinds, etc. but new content takes time to be made, and that's the reason for weekly locks and long grinds.

As other people have said, establishing the lock for a job and not for the character would be quite problematic to implement, people would fish gear with as many jobs as possible.