With respect to deactivating ejection seats there are two considerations. The first is if you wish to maintain the capability for a manual bail out via the manual separation mechanism of the ejection seat or by installing a static seat and using a conventional parachute. If so, is there an adequate egress route? Can the canopy be opened or jettisoned to permit the bail out? Is there sufficient space to get out of the cockpit, especially at high speed? If the cockpit access has not been designed for this abandonment case then such an option may not be feasible. Secondly, if it is a single-engine aircraft is the glide threshold speed low enough to permit an off-runway forced landing following an engine failure? For some aircraft such as the Jet Provost the answer may be yes. For high speed swept wing aircraft the answer will probably be no. So, if the glide speed is too high for an off-runway forced landing and a safe egress route for a manual bail-out does not exist then flying with an inhibited ejection seat would, in my opinion, be foolhardy.
There is one ex-UK military ejection seat type of which there are some examples flying on non-UK civilian register with inhibited ejection seats but with pilots wearing a manual parachute. However, this type does not have a canopy jettison system, the canopy cannot be opened in flight and the explosive canopy fracture system was not cleared for in-flight usage in RAF service because the pilot would suffer serious/potentially fatal injuries if it was operated other than as part of the ejection sequence. So how does the pilot bail out manually? And, therefore, in these circumstances why wear a parachute?! Again, my personal opinion is that taking such risks for recreational flying is not justifiable.