Unfortunately, there is no good compromise.
Last year, my wife and I agonized over XL hot tub vs. small exercise pool/spa vs. real swim spa. We did not have room on our patio for a dual zone swim spa + hot tub. We are long time hot tub owners and enjoy soaking, so we quickly ruled out a "real" swim spa for actual swimming because that would have taken all our space. So we looked at 12-14ft swim spas that were not really swimmable but had resistance jets, exercise attachments, 4ft or greater depth, and hot tub style seating.
Temperature was the reason we didn't get one. Unlike most hot tub owners, we do not like ours hot. We keep it at a temperature that is comfortable to soak in for an hour or more. That ranges from 95F when outside temps are >90F in the middle of summer, up to 100F when temps are <20F in the winter. The problem is that these temps are way too high for exercise. For light exercise, I'd want <85F in the summer and <90F in the winter. For vigorous exercise, drop it another 5 deg. Splitting the difference means high 80s in the summer and low 90s in the winter, which is going to detract a lot from the enjoyment of both activities.
The only way I can see it working is if you vary your usage seasonally, i.e. use it as a swim spa or exercise pool in the summer and use it as a hot tub in the winter.
