Engineer

Helo,
As you already know, ISRO doesn't relax it's criteria for recruitment (not even for reserved category aspirants).
But, there could be a workaround.
You should start preparing for GATE asap! Obtain a really good score and get yourself admitted to one of the premiere institutions offering higher education in your field (core specialisations), preferably, IISc or the Indian Institute of Space Science and Technology (IIST) situated in Trivandrum, or IIT Bombay. These institutes always have some ISRO sponsored projects that their professors and students are working on. If you could contribute to such projects, ISRO might consider you for a position. IIT Bombay and IIST have witnessed a lot of student placements in ISRO (don't know about IISc).
Despite the uncertainty looming over getting placed with ISRO, this route is still quite safe as a higher degree from these institutions will open a lot of doors. It will also help you assess your strong areas. Good luck!

Mechanical engineering is the discipline that applies the principles of engineering, physics, and materials science for the design, analysis, manufacturing, and maintenance of mechanical systems. It is the branch of engineering that involves the design, production, and operation of machinery. It is one of the oldest and broadest of the engineering disciplines. Mechanical Engineers are employed in Operations and Maintenance roles in Manufacturing and Services industry. It is an evergreen branch with no cyclic trend in job market. Some of the largest areas of employment of Mechanical diploma engineers are in productions, machine tools, railway engineering, aerospace, the automobile industry, power plants, armed forces and paramilitary forces.
You can chooses between B.Tech Mechanical Engineering or B.Tech CSE or B Architecture based on your skills and interests.