OK, I guess we'll just have to agree to disagree about that, then
Still, I'll explain my point of view:
I think plundering treasure fleets to find gems is a good idea, because it only requires turns, and cannot be "sped up" by throwing gold at it (although you can spend credits to get more turns). If another way is also used, like the NPC treasure hunt, I think they should both share that quality, yet they have to be different in some aspect. Making one way give you danger and another NOT give you danger, but require more turns on average, seems like a good way to achieve this.
Including a "gem mine" in the hideout is NOT, I think, a good idea. Then one can just "throw money" at the gems, to be able to acquire them faster than others. Keep in mind that richer players will STILL get more gems than poorer players, since they can buy gems on the market for credits (and credits can be bought with gold). This is as it should be.
Now, to your point that "only a few roles can find gems without using credits". First, I would think it was actually a GOOD thing if certain "roles", as you call it, found it simpler to find gems than others. As I see it, when you have several resources (like gold and gems), then one "role" should find it simpler to find one resource (traders may acquire more gold daily than other "roles"), while other "roles" should find it easier to find other resources. Alas, even with the proposed idea, this actually is NOT the case. As I have already pointed out, hunting down treasure fleets is equally simple for all roles, if you know how to do it. Secondly, finding gems this way will actually be MORE EXPENSIVE for "pirates" than "traders" for the following, simple reason: Finding gems costs turns. Traders hardly use turns trading, so they can spend almost all their turns looking for gems. Pirates, on the other hand, spend turns on plunder and skirmish, meaning that they have fewer turns left to look for gems. Put another way: To traders, turns have less value than they do to pirates, so by exchanging the same number of turns for gems, traders "pay less value" for each gem. This will become even more true with the academy "Piracy" and "Skirmish tactics" technologies.
Lastly, but by far most importantly: I wish there were more people involved in these types of discussions...