At this point I think it's pretty safe to say all merit ws's are pretty much needed by all players. Since almost everyone has 100% of the jobs @ 99, which is needed to participate with others. I think it's a good idea to increase the cap of max merits to something more realistic than...15. I mean you're saying only 3 ws's can be maxed. I personally find myself swapping between my jobs. For two months I'll play as brd, and swap over to sam for a few months and focus on that. Which is how a lot of players do it.
So I think we should increase the amount of maximum merits for to like 35, that's half of them 7/14. I mean idealy we would get 70 so we could just max them all, but even half would be nice. The main reasoning behind raising it to max is that we can now max out combat skills in all catagories, so we now are specialized into all weapons already, I fail to see the logic of having only 3 weapons (war by itself has access to way more than that, which they use all of) at max. At least having half of them maxed, we could keep all of our weapons on a single job up to date. As it stands right now I've probably wasted 10k+ merits switching them all the time. They cost an abnormally high amount to begin with, so I find it absurd that we have to keep switching like this.
I'm not sure how aeonic weapons really work, but maybe if you don't want to increase the merit cap, make the ws's unlockable (to their max meritable amount) through a quest after obtaining the upgraded aeonic weapons. It would help us make some good choices about what to merit based on the weapons we want to work to obtain.
I know this isn't the first time someone has posted about this, but we're entering a new system with merit ws's at it's core, and I think the system itself aught to be looked at once again and possibly fixed.