I know that ejection seats are good to help save pilots' lives, but they're not foolproof either and the design hasn't changed for decades.
Why don't pilots wear a squirrel suit or wingsuit so that they can fly away to open the parachute far from the enemy?
A wing suit has a glide ratio of only 2.5:1 in ideal conditions. That's no more than 20kms of horizontal flight, which means that you're not likely to reach any safe place.
Ejecting from a fighter jet is not an ideal condition. The odds of being knocked out be the blast, canopy or whatever made you abandon your aircraft in the first place are very real. Furthermore, ejection at very low altitude is not unheard of. This is why the chute is not deployed manually, and why the chute is not controllable like skydiving 'mattresses'. You don't want to tumble out of control!
Finally, you're carrying a small raft and some emergency supplies, all of which would not improve your glide slope. The jet is really the best method of reaching a safe place; ejecting is only there to reach the ground with most limbs attached if your supersonic get-the-hell-out-of-here vehicle is compromised.
Apart every possible aerodynamic consideration, wearing a wingsuit in the tiny space of a cockpit would be extremely difficult. In the F-16, for instance, there are instruments, switches and the ejection seat handle between the pilot legs (source: Wikimedia):
Limited arms' movement is another issue. Having parts of the suit randomly catching switches, levers, etc. will be a safety nightmare.
Also, many fighter jet's don't have explosive bolts that release the canopy during ejection, but rather some cordite in the glass to break it during the ejection sequence, like the AV-8B Harrier II (source: www.b-domke.de):
Passing through a shattered glass with the aforementioned wingsuit could tear off some part or lead to injuries to the pilot.
I assume you mean a wingsuit.
The idea behind ejection seats is that in a fighter jet, you are seating on tons of explosive materials (Jet fuel, munitions, ...). You want to get away from that as quickly as possible.
A wingsuit would be very inconfortable to wear in the cockpit during nominal flight, and it would be almost impossible to get off of the plane at high speed without ramming it, probably killing yourself in the process.
=> Ejection seat is the only solution for high speed/potentially explosive bail out.
Sail plane on the other hand don't explode and fly relatively slowly so jumping away with a parachute is doable.
You might ask why not using ejection seat THEN wingsuit
It would be impractical as it would only gives you very limited range (strikes can be done hundreds or thousands of kilometers inside hostile zone. And the ejection seat is so brutal that you would probably not be able to maneuver it properly after the shock of the ejection.
No, it is a 3 stage process. The concept would be to convert the seat chassis itself into some type of guided flying platform like a rocket jet suit.
1) The ejection process and auto parachute deploy would be the same as now.
2) Next after deployment the pilot while parachuting down has an option to just parachute down. OR if over hostile territory to further deploy a jet pack that separated from the seat and chute, and the pilot could fly away some distance.
3) There would be a secondary parachute that could be deployed miles away after flying the seat (jetpack).
