Welcome to Talk Morgan
A supercharged 1600 would be great but I imagine that you would definitely need to look at upgrades to the engine internals.
If the new Plus 4 that you drove was really very new the suspension improves after getting a few miles up. The current output from the factory is much improved over older models but the standard dampers that the factory installs are nothing special and better options are available.
Everyone has their own idea of front suspension improvements. Some are more interested in achieving the best handling for track days or racing and others are looking for more comfort for touring. I can only speak from my own experience.
I have fitted the Suplex RS kit with non adjustable Bilstein dampers at the front. It is a solution that offers optimal comfort, adjustable ride height, and good roll control. Others who have driven my car have commented that the car feels balanced and well planted on the road. For me it was a vast improvement over the standard Morgan setup and suits my needs well. Some have criticised the initial softness of the suspension that they claim gives a slow turn-in. It is not something that I find but then again I have never driven a car with competition tuned suspension. In your case I would suggest that you look at the race version of the Suplex front suspension which comes with a selection of springs and adjustable Quantum dampers. In that case the lowest spring rate in the kit is higher than that of the road version springs and it goes up from there. The race kit was developed in conjuction with the race team at Williams and I don't think anyone could say that the Williams 4/4 lacked in handling.
I also have fitted the Suplex 5L rear supension but in this case with Quantum adjustable dampers. The improvement in ride at the rear end is remarkable. I asked the designer to try the car on the way to an event at Castle Combe. Let us just say that to sit in the car as a passenger whilst someone who knows the road puts the suspension and handling to the test is an interesting experience

Unfortunately the 5L is not yet approved under the class rules for Morgan racing but if you were only interested in track days that would not matter.
Both front and rear Suplex kits are designed to improve the ride comfort of the Morgan with as far as possible also improving the handling characteristics. The Suplex front is already available in a track version and changing the springs at the rear to give a stiffer, more sporty ride is no problem at all, if that is felt desirable.
This is with the usual disclaimers about any financial interest. I am just a happy customer.
Something that may be worth considering is the
Plus 4 Baby Doll from the AR Motorsport division of Morgan.