The sprung wishbones is a doddle to execute once you've done the maths to get the right amount of it. The coil on the kingpin is not hard either - it's a simple bushing with an extra long bolt, spring and endplate.. I'd regard both as perfectly DIY. If you want suspension at both ends a delta is probably easier but does raise the front chassis right in your line of sight. Any bodywork will need to allow space for the pedalling action and may require a more upright seat than you would otherwise use to enable you to see over it because of that.
As a general rule:-
Delta - tighter turning potential
Tadople - better high speed cornering stability
You can make a tadpole turn tighter than SOME deltas and you can make a delta more stable than SOME deltas but you're at the extreme end of the spectrum for both of those scenarios.
As to simplicity, it's very hard to make a body that looks good, is lightweight and rigid let alone simple. You may get three of the four but all 4 is a tough ask. It usually requires plenty of craftsmanship to get the first three points. Those that do get made are very often the product of a home workshop. What base you start with will largely depend on what shape you want to achieve, whether aerodynamics is the most important factor or weather protection is and what skills you have with such things as plywood and fibreglass. If your skills there are insufficient then you'll probably be looking at making a frame and covering it with Correx or canvas or Cordura etc.
One thing you could consider is making a monocoque frame out of plywood and using that frame as at least part of the bodywork in a similar manner to these:-
The one above is rear steer and has front suspension. It's also FWD and much narrower than a typical tadpole as no room for turning front wheels is needed. It's much easier to add front suspension to a tadpole if it doesn't steer via the front. The frame is a simple affair but easy to add a canopy and front to by simply bringing the steering levers inside.
The one above has a LOT more craftsmanship put into the plywood. Note even the rear swing arm is a wooden box section. The builder has used the minimum of wood in as strong a way as possible similar to how an early biplane would have been made.