It's a mix of related ideas, certainly, to explain while I don't really have a strong opinion on the OP's statement. I was saying I would be unlikely to spend merits on Job Points as I spend them on HTBs. This statement was saying that even though I don't strongly support the OPs suggestion, I still think your argument was ridiculous.
In a manner, but you missed the entire point, you can't exchange exp for exp rings or for exp scrolls because it would be moot. Exchanging it into CP or JP would not. There are plenty of ways to change most forms of currency into gil, and even ways for you to exchange one type of currency into different denominations used for different things of it's own type which have different uses, and of course vouchers that change into most types of currency.
See the same argument when you say you can't exchange it for JP rings, or heck, could even say "You still had to use a Capacity Scroll, so no, you didn't exchange merit points for capacity.
To a logical limit that makes the majority of the player base happy enough to keep playing, but busy enough not to run out of things to do, which is the only logical thing to strive for in MMO design. I believe we currently gain JP too slowly, I can't state a concrete number, but I do believe doubling the amount of CP we obtain would do such, even over the long haul, could it be raised past that? Probably, but I wouldn't hazard an exact guess where the cut off point is for too much or too little exactly, but I feel we're a far cry away from that at the moment.