Thanks for the pictures of some fantastic creations using both Steck and System X.
The System X ones are sadly marred by the hideous and numerous empty connector holes, a problem which could be easily solved by Playmobil right now with a color-matched plug with some appropriate facade - a Tudor rose, a blank shield (possibly with optional stickers matching existing shield designs) a gargoyle or angel, a waterspout, a column top, a section of gutter, a hook for a hanging basket, a lamp bracket, or something like that. The Playmobil designers need to look at some real buildings and see what's what. The holes could be used to great effect to hold a frieze like the Parthenon in an ancient Greek temple set, or a Aztec style carvings for a South American lost temple for the adventure theme.
i.e. plug those holes, and you have a decent modular system to build with, if parts are made available in the right colors and shapes. We can live with the annoying red and yellow connectors because they're hidden.
As Giorginetto says, a collector who is building a unique structure using a modular Playmobil system is spending the equivalent of hundreds of normal buyers, and Playmobil should recognise this fact. Their new clip system creates a rugged building that can be carried in one hand if it needs to be moved, but makes next to no allowance for additions and enhancements to the original building, and for that reason sets using the system must be selling in far smaller numbers than either Steck or System X sets ever did.