It would be worth it if it was a simple swap....when all is said and done you will actually have less than a 4 stroke X6 or X8 seeings you will need a better hydraulic suspension and hydraulic brakes also 1pc rims like they have already....
you can use a MT Bike through axle hub laced into a double wall BMX rim then you can use hydraulic down hill MT Bike brakes for the front then on the back you can use pit bike rim sprocket and brakes.
The cool thing about mountain bike downhill Forks is you can adjust all aspects of the fork from the outside the rebound dampening and depending on the shock ride height control lockout and other features that will allow you to easily tune the fork to your riding style
Just make sure it's a downhill mountain bike fork and not a cross-country mountain bike Fork cross country Forks are light-duty and designed to be super lightweight and are not nearly as durable as downhill mountain bike Forks that are designed to take massive unbelievable jumps and drops
you cant use the stock back wheel it will rip the bolts holding the sproket right out of the rim (even the pit bikes have this problem)