When I first saw this pen I thought easy to modify! You can easily scrap the end piece and turn your own that will still allow for posting of the cap and your have no ugly threads on the end of your pen when capped. I see that as a big bonus!
I also thought the finial could be easily pressed out and a custom one inserted to match the pen body. It turns out it is easier to do. The finial screws into the cap. You can loosen it by posting the end cap and then twisting the finial and it will unscrew. I found that out by accident.
I too had concerns about the threads at the front of the nib section but they seem fine when held. Most nib sections have some sort of "back stop" so that you do not slip off and this is no different.
Also. I am trying to get the tap size for the nib section so that we can get rid of the front chrome piece and that would make for a very nice looking pen. I'll let you know what I find works or does not work.