So, noone wanted to sale me his Waveform City, now in 2015, and they are right, this "obsolete" module is essential in the Wiard system. Basicaly it is a Classic VCO with a wave table lookup system (like the Blacet Miniwave).
By chance Blacet Research still sale the miniwave in kit (http://www.blacet.com/MW.html ), and I own 2 classic VCO. I wanted initialy convert one to a Waveform City and had to sacrify few fonctions... but, why not build a little tile panel for that and the Blacet miniwave inside case ? This will be the Waveform City X ( X for CVCO expander).
The miniwave have a long story, Miniwave, Monowave, Waveform City, Megawave ( http://www.infinitesimal.eu/~modules/index.php/Malekko_Megawave ) are all based of a wave table drived by an external signal, it converts a basic VCO into a wavetable VCO, can process signals, can work like a quantizer, lot of other applications. For further information about the miniwave, check out that archived page by Grant Richter : https://web.archive.org/web/20130808091908/http://www.musicsynthesizer.com/MiniWave/MiniManual.html
The kit is easy to build, and I made a panel, here is file (in addition there are 7 eurorack blind drilled panels), the file is free : http://www.ponoko.com/design-your-own/products/wiard-blacet-miniwave-waveform-city-x-eurorack-drilled-blind-panel-12766
designing the panel :
leds into the panel :
the Blacet PCB into the case, with the regular ROM and the Socket Rocket :