As the old saying goes. You knows what happens when you assume. Might suggest going for a fitting. The new GT2 is an awesome club. At least try it. Not knocking the TSR. Was playing the TSI and moved to the GT. Am playing a TSR fairway and Hybrid, plus a GT three wood and hybrid. All shafts the same Driver to hybrid. Fitter set me up.

Us hackers really can’t offer you informed recommendations. We don’t know your swing

There is a retail outlet - Dallas Golf that might be able to fit a shaft for you for a TSR-2 head. Titleist fitters only fit the current GT woods (with the next release due next summer). There are those that use the same shaft, the next shaft weight for the shorter fairway, or use a different shaft altogether. Can’t say where you fall.

The driver and fairway hosel fittings are not interchangeable. So you wouldn’t be able to try your driver shaft in a fairway without changing the hosel adapter. If you were to buy a Ventus shaft alone for a TSR fairway, how would that compare to a new and fitted GT fairway with that shaft included.? Often the aftermarket shafts compete in price with a fullly built head and shaft from the OEM.

If you're going to buy a new 3-wood, and are committed to going Titleist, why not do the Titleist fitting process? Granted, even with rolling the $100 fitting fee into the purchase price, a new GT2 is going to likely be more expensive than the TSR2 you've mentioned thinking about. But, you could try GT2 vs GT3, dial in lofts, head-weighting. As well as try V Black, the new V Black+, TR Black, or other shafts entirely. I like the original V. Black w/Velocore, but I have to admit the Tensei 1K Black---for me---is honestly 90-95% as good at a much lower price.

As a very rough guess, and realizing you might hit a tee-only club like Driver differently than a 3-wood, starting out with another V. Black, same flex, and bumping the weight by 10, all might work too.

If you are going to spend the money get fitted again as it might be different with the wood.