When doing high-end reproduction work you should use Linear or Linear Scientific and an Object Level Target like the
ISA Targets. If using Linear you should be aware there is a slight roll off at the high end of the tonal range, so you should set your exposure based on middle gray and not light gray. This can be useful when shooting higher gloss subject matter and you are not, or can not cross polarize, since a gloss in Linear Scientific can lead to weird artifacts in transitions between blown and nearly-blown tones.
The loss of saturation is because the default profiles in the general purpose version of Capture One are geared toward use with a curve in general purpose photography. If you're looking to match the quality produced by
The Getty, Library of Congress, Smithsonian etc or are working with clients looking for
FADGI compliant reproduction then I'd suggest
Capture One Cultural Heritage Edition which come with bespoke color profiles for cultural heritage imaging (e.g. art repro) which are meant for use with linear curves and also include LAB readouts which can be used to validate the response curve and AOI of the Object Level Target to confirm perfect exposure and perfect linearity.
