Just a quick heads-up that the climbing system taught by TCI is cheaper, easier, and safer than what you have drawn. If you have already invested in rope, pulleys, carabiners, and pantins, then I strongly encourage you to invest in yourself by at least buying a copy of the TCI Tree Climbing Basics DVD (for less than the cost of one triple-locking carabiner). Ideally, you would also take a TCI climbing class. They're cheap, don't take much time, and are a lot of fun.
I would discourage anyone, new or experienced, from using the system drawn below. My understanding is that prussic knots were popular in the early days of mountaineering, and while they still have their place for non-life-support (attaching a rope footloop, for example) there are much more reliable knots and climbing systems now. (When I say "more reliable," I mean friction knots that more reliably hold when you need them to, release when you need them to, and are more stable and don't capsize/bind. So, better in every way.)
Lets break it down a few other ways.
#1: strength of links in a chain...
A chain is only as strong as its weakest link, right? If you hang a chain from a rafter, and you clip a bucket on the other end, and you keep filling the bucket with bricks, every single link in the chain has to be able to hold up the whole bucket. If even just one link fails, the whole bucket falls. But when you are climbing, the bucket is you, and the fall can hurt or kill you.
#2: number of links in the chain...
If your chain has two links in it, or five, every link still has to hold all the weight of the bucket. Why use five links when you only need two? It seems to me like that leaves three links that you need to inspect and trust for no reason. (I look at your drawing, and immediately want to eliminate the pulley, the upper carabiner, and the separate rope for your bridge... aka "split tail.") Not only that, but nobody should ever use a carabiner up at the top that way. That is absolutely not a safe way to use a carabiner for many reasons.
#3: price of TCI system vs. this drawing (conservatively):
Eliminate the upper pulley: -$39.95
Eliminate the upper carabiner: -$18.95 (as I said, terrible use of a carabiner anyway)
Use a cambium saver instead: +$23.95
Eliminate foot pantin: -$64.00 (or more)
Save that rope you are using for your split tail, and turn it into a footloop: free
Use the tail of your climbing rope to tie a better bridge/friction knot: free
Total savings: $98.95
Even if you buy the TCI DVD ($19.95) you'll still have $79 left over!
This just saved you almost one hundred dollars, I made your system easier to set up, and I made it more reliable, easier to inspect, and safer.
Anyone else on these boards nervous about climbing on a prussic, worried about Chiutai's safety with the system he posted, and worried about a drawing like this encouraging someone who is just starting out to climb dangerously, more complicated, or more expensively than necessary?
We share your concern. However, we do not want to start censoring our Forums. We watch very closely for what gets posted, and most of the time we or a another experienced climber replies when something looks sketchy. You'll notice that we recently put up a "sticky" at the top of each Forums page advising newbies to get good training; it's important to keep reminding them not to try everything they see here unless they absolutely know what they're doing.
Keep everything in your support system life support rated and as simple (balanced with the function you want) as you can. You will find what works best for you. Keep a phone on you so when that presik locks up you can call to get help down.
...and getting professional training may be what helps you most.