So what is the problem here? What yyzdub says is pretty accurate it seems.
My own experience of the contract world, is that it can be a bit brutal if you don't know what to expect. Having said that, anybody with a modicum of intelligence should realise that. You know where you are going, you know how much you will be paid and what is included in the package. There is no way you can complain if the airline wants to get it's money's worth.
The other point worth mentioning is that, in my time in the contract world, I came across quite a few pilots who were more than happy to screw their employers, so it isn't a one-way street. I also know that the contract world can attract pilots who can't make it as career pilots in larger airlines for one reason or another. Some I have flown with were barely competent, others had the personalities of rodents.
My take on what I have managed to find out about Sigmar so far, is that they are far better than average in the way they select and support their pilots. The people running the company are experienced industry players, and there are several pilots amongst them, so they know their business. It turns out I have met one or two of them before in my travels, and they seemed pretty straight to me.
In addition, they are part of a large employment company and have some serious backing.
From the information I have so far, it is clear that they go a lot further to protect the pilots they have in the field, than most companies I have dealt with in the past. They also appear to have good support networks.
Now none of the above is meant to imply that they are the best thing since sliced bread, it is just what I have found out so far. I have no relationship with them, I am just an interested bystander. The information I have could be wrong!
One thing though, if you want to leave a contract and the company witholds your passport (why would they have it in the first place???), yyzdub is right - just go to your embassy. You don't have to hang around and wait for it to "appear".
As I mentioned, the contract world is for grown-ups.