Really the only thing the M3W might need is a filter in front of the injectors. Several thousand of these machines are running around with only the sock type filter in the tank and the number of people reporting injector issues are next to nil. Fuel pumps...that's another story.
The current setup does provide a high capacity filter with pressure regulation, so not sure the gain from changing that out. The filter flow capacity is sized for a much larger engine than the M3W so flow capacity shouldn't be an issue.
Regulators can be installed before or after injectors, but are more typically installed after in a return type system. Regulators before the injectors are typical of returnless systems (which is probably a bad idea on a large air cooled motor which blocks airflow to the fuel lines). I believe MMC prototypes used a returnless system before changing to the current return type setup.
