I don't really think it's possible to create a human mineable coin. The problem is you need a PoW algorithm which is hard for bots to solve but easy for humans to solve, but it also needs to be easy for computers to verify the solution. There is no easy way to meet those requirements. The problem space would have to be so huge that a bot wont have any chance at finding a solution by randomly searching for one, but it should be solvable by applying creativity and logic. For example when a programmer is faced with a problem he must apply creativity and logic to write an algorithm which can solve the problem. If he were to randomly try every possible algorithm he would never find a solution, but by applying human reasoning skills he is able to write an algorithm capable of solving the problem. That is the sort of PoW problem required to make a human mineable coin.
It does not need to be a 'solveable' PoW. When for example two or more people compete in a game they are matching human qualities against human qualities. A 'game' context would also solve the language issue since anyone could mine without knowing a specific language.
In general terms I will admit that you are a developer and I am not so I can't answer very well your points. But in this instance it is a fresh enough concept that the limitations you might see could be solved simply by starting from scratch. The only things to be taken for granted are 1) an electronic currency 2) mineable only by individuals 3) without regard for the level of tech they can afford etc.
A person should prevent it from being a gambling currency, in other words some purpose and skill should be involved. Aside from that it isall developer issues and problems to figure out how it could be done. Out of my depth ha ha.
By the way the majority of devcoins are essentially mined by human creative work: 180M coins were distributed to people who earned shares for developing open source software, completing bounties, writing on devtome, which pays 1 share for between 700 and 2000 words according to writer's quality. The number of shares acts as the effective difficulty in earning devcoins, which is getting harder and harder (just like bitcoin mining). The coin has been around for more than 2 years but devtome is a fairly recent addition.