I am so happy that this thread turned out to generate so many very interesting remarks and suggestion! Thank you!
First of all, I must try Canson's Platin Fibre Rag. From what you write it seams almost ideal: no FBAs, big gamut, excellent white point, high dMax, 100% cotton, acid-free and buffered... How does it compare surface and gamut wise to the other two contenders mentioned here, Canson's Rag Photographique and Museo Silver Rag? BTW I rely heavily on your observations, because in remote places, outside of Europe and America, Museo isn't well distributed. And planing to try out any new paper implies considerable investment of time and money to bring it here.
Regarding my original intention to varnish a print and to leave it without glass, I understand that the varnish and the way to apply it, is the weak point. But Golden's MSA varnish has very good reputation especially concerning yellowing. "Aging Characteristics: Accelerated and intensified aging tests of this varnish indicate it resists yellowing and will not become brittle under long term conditions of interior exposure." (quote from http://www.goldenpaints.com/technicaldata/msavar.php
Also there will be a lot less reflection than when the print is under regular glass. In addition to any reflection from the print and the glass, the reflection of the print on the inside of the glass and back is what bothers me. (Real anti-glare glass is simply too expensive here. As it is not available, I would have to import it
Very new to me is the idea, Ernst Dinkla, expressed, to consider the varnish (or parts of the coating, as in the Ilford Galerie Smooth Pearl) as something like an encapsulation method for the OBAs, sorry the FBAs ;-) I have to think about that. Thank you Ernst! Maybe an encapsulation in varnish, front and back of the print would be interesting?