Dear mehdi343,
After reading your project description I conclude that you are in need of an arbitrage bot to trade between BTC/LTC.
I have created such a bot for personal use and am interested in selling it. The back-end is personally written and I would say fits 90% of your criteria. Settings and thresholds are all written in the code instead of changing a text file with settings for instance.
The application itself has an intuitive GUI and one simple "trade" button to execute trades simultaneously on 2 exchanges. I never got to the feature of auto-trading though. If you are interested please let me know and I can give you more information should you require so. I am also interested in knowing what your budget is regarding this project, I am willing to sell the software in its current state but want to add that there are probably a few points that need to be addressed to have it entirely to your wishes.
Thank you for your time,
Best regards,
Jeffrey Pijnappels