Thanks a lot for your inputs. Yes, I agree Abel makes a good refelt work. My intention is to change also shanks and flanges (I have a semi-new set from Renner full compatible with the old ones) so new hammers is my choice. If I read correctly Weickert felt (made in Wurzen fabrik) was probably the original felt hammers in the most vintage german pianos (before WWII). I also read marvels about the recent ones (André Oorebeek included). Anyone has tested them? (named "Renner blue point" in USA)
The felt is only a part of what determines the working characteristic of a set of piano hammers. Starting with Weikert felt a hammermaker can come up with a variety of weights and densities of hammers. Hammers using the same brand of felt can end up producing tone qualities that vary dramatically.
My favorite after-market hammers for pianos like the one you’ve described are made by Ronsen using Weikert felt—For some reason you’ve ruled them out.—but it would be quite easy to produce hammers using Weikert felt that were rock hard and completely unmusical. All that is needed is a lot of compression and heat.
On the other hand it is possible to make quite nice hammers using felt of lesser quality if the hammermaker is careful to control the shape of the felt strip, temperature, pressure, the amount of felt compression, etc. Don’t make your hammer selection based on felt alone; it is certainly important but it is not the only important criteria.