First i need to say i dont have a fruiting loquat tree, and have been growing loquats for 2 years so thats from my very limited experience...
The plant may be a seedling ,dus may be young to be fruiting ...also i see tree different stemms which may be tree different seedlings that have grown so close together. I personally would remove the middle one, which is the weakest judging by the pics.
You are asking about grafting it, i would personally do that bud still would leave a branch from both of the main trunks, since they may end up to be something special. Be sure to use scions from a known fruiting loquat with nice fruit.
This spring i grafted a dozen of loquats on quince, i used cleft and bark graft methods, all were succesfull and loquat by me seems to be an easily graftable plant.
Now u may also wait a little more on the plant, it may be just too young to fruit, that is if the problem is not hiding elsewhere.
Has the plant ever flowered ??