So, as promised, a short update... After talks with 2x different BU's, the sobering truth comes. Without an input plan, nothing works. They do have a planning office they work with, but only next year...
Is it really that hard to find a good architect whose price fits and who is also interested? I will simply talk again with the 1st architect and see how his price is composed and if there might be a little room for negotiation.