I cannot tell from the picture the make of spa jets. They look like standard spa jet eyeballs. The nozzle is deep inside the spa and that is one thing that can be reduced to help increase the force. However, I would get the builder involved to make sure you get the correct nozzles.

From the picture, I cannot tell which of the two pipes or both are the air intake. If you have a single 1 1/2" air intake, a blower may help since it is such a small pipe. However, from your spa picture with the jets on, it looks like there is enough air in the stream so I suspect the air intake is from the 2".

Do you have a shop vac? One good test is to switch the shop vac hose from suction to exhaust and have someone put the exhaust hose into the air intake of the jets and push extra air into the pipe and see if that helps the jets at all. You may need to seal around the hose with a rag so air does not escape. You will see more air come out of the jets but it is unlikely that the jets will be stronger.

One thing to be aware of is that blowers are quite noisy and are best used near the pad, far from the pool, and not where you currently have your air pipes. So I would make sure that you really need a blower since the work and cost involved will be quite substantial. However, I still don't think it would help much.