> At this stage I think it would have been faster, cheaper and lower risk to have either developed a launcher that could have fit it inside a fairing with a more conventional and less compact shield...

They are, for a generous value of "they". For the cost of making this observatory fit on an Ariane 5, SpaceX is developing a 9-meter reusable launch system that can be run in a carbon-neutral fashion. It would still require folding, but nothing beyond conventional folding techniques that have been used since the 1970s.