One of my favorite parts of pool construction. Not only must it look good, it must run good. All show and all go.

Upgrading your pipe size will allow the system to run more efficiently and reduce water velocity and increase volume. The upgrade will support new systems and allow greater flexibility on equipment choices.

I don't know if your pool is vinyl or concrete, so replacing the entire run of pipe for the main drain will not be possible short ripping out a portion of the floor to do so.

If it's a vinyl pool and you plan to change the liner, I would change the main drain to a 2" size and add a second drain set 3' apart on center. The "tee" connection between the 2 drains would 2" and on original pipe connection (assuming 1.5") reduce to existing size.
The new drains have the VGB approved covers. If there's no way to add or change the drain, replace the existing cover with a VGB approved cover. If the pool is to remain filled, hire a diver to change the drain cover.

On our new construction we use 3" PVC on our bottom suctions. We actually have stopped using main drains and opted for VGB approved strip drains set on the back wall.

If you can find the end of the drain line at the pool side, increase the pipe size to 2.5" PVC. It's not worth going to 3" as the original pipe is only 1.5"

Increase the skimmer pipes also to 2.5" .

The returns can have a main 2" pipe run to the pool, and split to feed returns a 1.5".

We create a loop plumbing to allow even distribution to each return, and skims too, for even return and even suction. I'm not sure of your existing plumbing layout.

You can use valves to regulate skims if a loop plumbing is not feasible. Returns can have sized eyeball fittings to regulate flow at each distribution point.

We prefer a pressure side cleaner which uses 1.5" pipe. Not a fan of suction side cleaners.

The 60 SF filter is fine. Bigger is better in this case with filters. It's when pumps are oversized that problems can occur. Piping must be large enough to accommodate pumps and allow them to work at their maximum efficiency.

The illustration I give my clients when pumps are oversized and pipe is too small, "It's like sucking water through a cocktail straw". You need the supply to allow for proper operation. Unfortunately, I see this more than often even new pools.

ALL PVC PIPE MUST SCH. 40 RIGID!!

Have your contractor use a high quality valves at the equipment such as a Jandy Never Lube type.

I wasn't planning on changing all the unground pipe just where all the pipe comes out of the ground i.e.: where main drain and skimmer 1 1/2" lines come out of ground combine at valve. Instead of 1 1/2" out I would plumb 2" to pump filter .Do same (Start out 2") for returns since I would be feeding two 1 1/2" lines. One for the three returns and one for pressure side cleaner/ I would be drawing and feeding more water to branches. All out of ground piping would now be 2". It was all 1 1/2" .

Understood. That's fine. I would however reconsider the VS pump as you will only get the benefit of the very low speed as the piping is only 1.5". VS pumps are not for everyone.
Consider a 1/2 or 3/4 HP pump at the most. It won't draw much power and it can handle the amount of water supplied to it. Trying to draw too much water will cause the pump to cavitate or draw more air than water. A general indication is air bubbles in the pump basket during operation.

Excellent, Thank You