I have seen some really good FPSC screen shots of some peoples work to be fair.
I think of myself as a pretty good game designer though without doubt there are many better - with respect before asking for someone else to show us how it can be done. We, myself included need to perhaps lead the way - but thats not at all the point.
To be honest FPSC is designed as a click and play game making environment and many users have shown a great deal of ingenuity in many ways already in pushing the boundaries of it in many different ways - level design included.
That kind of user is always going to be in a minority and is so at any indie game making arena.
As far as advanced level design goes currently thats almost a non starter for 10 as the editor and engine and its issues are just too restrictive. With enough hard work and effort - say some considerable number of years of it - you could possibly achieve high quality content throughout but I dont know that you can expect FPSC to run it without grinding to a hault - even with the most vigorous optimisation methods.
Firstly the current map object and script limits will make it impossible to achieve anything like a modern advanced game title quality and will quickly stop your game dev dead. Apart from anything else - while they exist it cant be done.
FPSC is a good engine in many respects - those that its good at - like painting straight walls - very good at that.
As anything like an advanced level design and game creation system it falls well short in most respects required to meet with modern gamemaking standards.
Out of the box, FPSC is an FPS Quake 2 kinda style and quality game makeing product - minus those things it cant do that a Quake 2 editor can and some perhaps that they cant. So its not really designed for or capable of advanced game creation as it stands.
Those who want to push the boundaries can do quite a lot to improve the kind of game that can be made with it - but ask anyone who is already working with advanced game design with FPSC and they will tell you how hard it is to achieve - everyone knows that this is the case so I dont know why people ask this question.
Making an advanced game with great level design as suggested takes many years of hard work so you are not going to see big strides in the short term with an engine which does not have the capabilities, functions and features to easily allow it to be achieved.
Shear hard work and a lot of effort will return results for only a few.
As said I have seen many good looking screen shots of levels and games people have worked on and I applaud them all for their hard work and endeavours and wish them the best of luck and success with their future gamemaking.
I do hope that all users will see an improvement in the product to the benefit of the games made with it.
"I am and forever will be your friend"