I understand one of the stumbling blocks is in the maintenance - How can you guarantee that the replacement parts match the original items the safety case was drawn up against?
Say, for example, part of the fuselage needed changing and L3 swapped it with a part off the rest of the RJ fleet which had an incomplete history and completely different flying hours, then what happens.
As to the reason for going down the RJ/Airseeker route instead of the original Helix upgrade plan - I'd guess that when Helix became unaffordable (due to them realising that extending the R1 was not solely it's current running costs because of the infrastructure support it enjoyed from the maritime variant?). It looks like they revisited earlier, pre-Haddon-Cave, proposals without fully considering the implications.