Welcome to the board. It is commendable you would seek more factual information by selecting this board, albeit, not necessarily this forum.
It is a bit interesting to consider creating fictional ideas which we can debunk
prior to publication.
Hmmm...but that's like..."we can tell you, but then we have to shoot ourselves."
Oh well, I’ll try to help a little but I’m no scientist...
Basically, you need immense hydrogen density and temperature to get fusion to work. With enormous gravity, you get both as the pressures in the core becomes hotter and hotter as a would-be star acquires more mass which increases the total gravitational force.
So either you get more mass for Jupiter (80x more) somehow, or you change the conditions to allow nuclear reactions at low densities. The later will require you to reduce the electrical charge on the proton in hydrogen to allow it’s nuclear force to grab hold of it’s neighboring proton which releases energy. Quarks, I think, are responsible for charge formation, so, if you can dream up some kinda new quark that neutralizes electric charge you might get a quick blast.