Fixing wrong concrete spa plumbing advice please

Can i get some advice on plumbing a Spa.

I am helping my brother finish off a spa which the contractor was messing up.

There is currently 1 main drain and no skimmer, (a vac line was placed through the shell, which i will convert to a strip skimmer and connect with a T by the spa wall.
Therefore i would have two suction lines running back to the pump room on a single 2'' pipe.

There are 6 returns, 3 at the top and 3 at the bottom on one manifold running back to the plant room on a single 2'' pipe. There were no jets, Venturi or otherwise installed whatsoever.

My plan is to use the bottom 3 returns for filtration by separating them from the top 3.
Therefore the top three will then run a separate 2'' pipe back to the plant room and i'll use this manifold for only 3 jets which my brother is happy with. I will probably retrofit some venturi jets into the top 3 new jets at the back of the spa wall.

My question is will i be able to have the 3 new jets draw from the main drain/strip skimmer suction line which will also be supplying the 3 returns at the bottom of the spa.
Or should i add an extra suction line dedicated to the three jets alone, perhaps taking one of the 3 planned returns at the bottom of the spa and making it a dedicated suction line for the 3 new jets.

Hope i explained well enough to understand.

Regards

Matt