Not that... It depends how strong your fan is. if it moves the others by airflow alone, they generate electricity. A generator is the same thing as an electric motor, more or less. If you pass current, it makes the axis rotate. If you rotate the axis fast enough, it generates current. You don't want current flowing back into your controller board/psu.

Take a tester to measure voltage, plug it to a disconnected fan to the ± pins. Now make that fan move by pointing another fan to it, and see the results.

I never quite understood why asic miners used this tunnel design with two fans pushing/pulling one another, but it seems Bitmain has improved the design, perhaps after the R4 experience.

If both fans are moving about the same amount of air, there shouldn't be a problem. But i don't know how powerful your squirrel fan is. I think it would be ideal to just remove the small fans, as you originally intended. Problem is you need feed back rpms to the controller so it doesn't complain, at least until Braiins OS is ported to the S15.