I think you would be wasting your time and money. The reason a 2" drain is required for a shower is that if it was just a 1-1/2" drain and bcame becomes even partly clogged, you'd have a flood. The larger 2" drain gives much more opportunities for the water to drain. If the tub drain clogs, you have the tub itself to act as an emergency catch basin. I have a tub-shower combination, 1-1/2" drain, that has never clogged in 37 years. Your tub is designed for a 1-1/2 drain so to go larger would require figuring out how to cut the tub outlet larger and finding 2" drain hardware.