Hii

The Low Speed Area solution (LSA) places a limit on the speed at which a forklift circulates through different areas of the warehouse.
This system is specially designed to reduce the speed of the trucks in areas with pedestrian activity or where others are working.

It totally depends on the business and the number of orders it is going to process in a set interval of time. Though the foremost priority is the safety of the inventory still there is enough room for increasing the speed efficiently.

I think there won't be any speed limit for warehousing operations. Some companies set their own speed limits to increase their productivity faster.

There is no modification to the cab available to increase visibility.
If the truck is handling bales then visibility is bound to be decreased by the load in front of the truck.
In this case the truck should be operated in reverse.

Don't believe there is an industry standard for truck speed operating inside. This would be the responsibility of the plant operator. Some plants have pedestrian lanes where the truck is not meant to enter. Other areas are no go areas for trucks or pedestrians.
There are quite a few companies that offer speed and zone control. It's an extensive subject today due to the growth of health and safety. However, multi-speed systems are not as easy to have on a forklift or warehouse truck as you might think.