Disassembling an EX4 file may run into copywrite and legal issues. It would also be difficult if you do not understand the way the ex4 file is integrated into MetaTrader4. It most likely uses a virtual machine/interpreter to take the contents of the file and use it. So then you would have to disassemble it and figure out what commands it is giving to MetaTrader4. It would take a lot of work and research to do it and it would be prone to error.
HFT it is an other way of trading and every institution has own secert HFT strategy .
The good thing in forex is that you can invent your own unique strategy that nobody know before you . The problem is you dont know when you will find it ?
After 1 week or 1 year or even 15 years . As long as you keep try , by probability, you will reach , only death can stop you