The main limitation of the wipers on the trad Morgan is the extremely low height of the screen. To fix this would need a complete redesign of the car which would probably involve moving the base of the screen further forward and inclining it more, perhaps even (

) using a slightly curved screen. This would increase the possible length of the wiper blades. The current length is, if I recall, 7" but to get some sort of modern blade it would be necessary to go to at least 10" if not 12". These are sizes that are generally only used at the rear on modern vehicles but there are some modern blades available which could be suitable.
The other issue on trad Morgans is that Morgan, in a very lazy way, make the position of the spindles exactly the same for left hand drive and right hand drive vehicles. The spindles should be offset towards the driver's side and the blades should park flat towards the passenger side. At the end of its stroke the driver's side blade should be vertical and virtually next to the windscreen pillar. This would leave the least obstructed view for the driver.
I note that the wipers on the PlusSix are offset in the way I have described so perhaps after more than 60 years of producing the round cowl shape they have worked out the need for some improvement in the driver's wet weather view.