Theoretically, it is possible, but far from easy. First, you have to replace the dual 24/16MHz crystal with a dual 24/20MHz one, if one exists, or connect a 24MHz and 20MHz crystal. The CPU and the ISA bus use the frequencies derived from the 16MHz crystal, and the PSSJ sound chip uses the 24MHz crystal.
Second, you will need to replace the CPU, NPU with 10MHz chips and the RAM with an access time that can handle 10MHz access @ 1 wait state.
8MHz is something of a barrier in 286 systems, as cards on the ISA bus tend not to work reliably if they are accessed at a speed greater than 8.33MHz. So if your 286 is running at 10, 12 or above MHz, your cards may not run reliably. In fact, any access outside the memory or coprocessor may be unreliable. This was taken care of in systems designed to work at 10MHz and above by logic that added extra wait states to I/O access. The TL would not have this logic.
