Greetings employer.
To make this as short as possible..
In order to make this keyboard as You noted in description, one would need an team of experts and a well equiped facility with expencive equpment, so there is no logic in doing that since it would cost a fortune to do that.
Best thing You can do, in order to keep the old keyboard with touchpad for Your personal pleasure, is to order a conversion adapter that is actually cheap to buy.
If the keyboard has to be pressed hard in order to write a letter, it means the metal contacts inside have been worn off and You can just dump it in the trash.
If You write on keyboard and suddenly it stops writing for a few seconds, it means there is a problem with PS/2 plug, cable or keyboards electronics that makes comunication with PC. If the pins on PS/2 jack are bent or broken, You can just replace the jack. If the cable is bad, You can replace that too. If theres any other issue, its non repearable or too expensive to be repaired.
I hope that this gives You clear insight in the problem and better understanding of the keyboard problem.
So, if the keyboard is functional but You just want to plug it into USB port, there is a solution to that and You just need an adapter that is cheap.
Feel free to contact me for any further detail and help if needed.
Regards.
CroatianGuy