The suggested change to ...

The suggested change to straight series pumps will work but the controls are likely to be more complex and expensive. The problem is that you have to ensure the suction pressure is high enough to meet the NPSHr requirements of the booster pump as the flow from the booster pump to the final distribution chamber will change as the level in the distribution chamber changes.

Since the current installation pumps from the well to a sump, I'm assuming there is not any excess head available on the well pump. When you put in the in-line booster pump, you may have to increase the well pump's head to keep sufficient suction pressure on the booster.

A VFD on the well could be employed however retrofitting an assumed constant speed pump with a VFD drive doesn't always work well if the pump is not designed to be VFD driven. In order for a VFD to work, you'll probably need to install a suction pressure transmitter at the in-line pump and send a signal back to the well pump. Then you'd need a PLC or some type of controller to adjust the suction pressure of the in-line booster pump by varying the speed of the well pump. This would likely be a major expense with telemetry costs.

An old school but less economical solution would be to install a bypass PRV at the well and set the discharge pressure at the well to a constant pressure determined to keep the suction pressure at the booster pump within acceptable limits. This could also be done with a VFD. This recommendation would only work if the pump operating point could be moved to the left to generate higher head to supply the increased suction pressure requirement of the booster pump.

You'd likely need a flow control valve at the distribution chamber to set the discharge flow at a constant value. The problem to deal with is making sure all the pumps discharge at the same flow.

Without knowing the elevations of the pumps and tanks along with a full description of the components and operation, it's difficult to make a informed recommendation, along with pump curves. I'd suggest that if you don't have hydraulic modeling software, download a copy of EPANET2 and create a simple model of the system. Then see what happens when you switch to an in-line booster pump from a sump pump.

Solving the land use problem would be the best solution but with enough money any problem can be solved.