Replacing I/G 20x40 vinyl liner

This pool was originally installed in 1970 , has 2 return lines and 2 skimmers, the walls are steel and the bottom sand.
We had the liner replaced about 12years ago, and the company that did it said we didn't really need a main drain, so they removed it. After 12 years of cleaning and researching i think that may have been an mistake, and since we are replacing the liner would putting in a main drain be a good idea ? . I have heard of diverters(eyeballs) that screw into the return lines and the water diverted to the bottom to keep debris moving and circulating so it can get to the skimmers and get filtered out. We plan on doing the work ourselfs, just looking for some guidance/advice to make sure we get done what needs or should be done. We are also going to an automatic cleaner this year, no definite decision yet but looking at polaris 360. The place where we bought the liner from recomended going with diverters(eyeballs) and the polaris as an alternative to putting in a main drain.

I'v seen wall pading for the sides, and was wondering if the same could be used on the bottom also. i think it would give the bottom a nice soft feel.

thanks much

We replaced the liner on our 18x42 vinyl in-ground 04. The pool was built in 82 and we have 2 skimmers, 2 returns, 1 dedicated vac line in the wall and a main drain. The liner guys never properly replaced the gasket in the drain (or on the skimmers or the light fixture) and this is one, among many, reasons the pool has leaks. We put a winter plug in the main drain and would like to eventually get it repaired properly. The drain does make a big difference when cleaning, lowering the water level, etc.

We had foam lining put on the walls and the stairs (our liner goes over them). For the first year the steps were really comfy - and the top one of the three still is. But interestingly, the foam on the middle and bottom steps has completely been crushed by the weight of the water, so I don't advise using foam for the bottom of your pool - it will be an expensive and short lived benefit.

Plus, the foam makes the liner more vulnerable to punctures - something we learned AFTER having had it installed.

Good luck!