And the best ways to overcome them.
Developers: I see the developers as being the ringmasters in a multi-ringed circus: attempting to make everyone happy, despite the compromises in design amenities, etc., which must be implemented. Issues which seem simple — say, parking — can become a Rubik's Cube. Residential users want sequestered and reserved parking, retail users want easy access and few restrictions on parking and office users need both reserved and unreserved spaces, as well as ample parking spaces for visitors. Validation process for guests is an open item as well. The inherent conflict in these and similar goals makes the project challenging.
Investors: With few exceptions, most investors like the Idea of the synergistic value which a mixed use project can provide, but do not want to own assets which have mixed and blended uses. So creating clear and discrete parcels, which isolate a use (e.g. hotel, etc.) within a mixed use project is important Investors are also concerned to confirm that the allocation of operating costs within the mixed use project is reasonable, fair and predictable.
Designers: Mixed use projects present challenging building code issues, and require care in dealing with the local municipal authorities. Often, "Life Safety" Issues require considerable attention, given that the different "buildings" within a mixed use project will be interconnected and therefore at variance with standard set back and separation standards. Fire escapes for "Building A" may be provided via corridors in "Building B". Also, providing for 3D perspectives is necessary given the conjoined nature of the overall project scheme. The CAD systems are utilized to their fullest capacity.
Contractors: As with any large scale commercial project, the contractors must make sense of the design and plans, and often face in the field challenges which were not previously envisioned. Phasing and scheduling are particularly difficult, along with maintaining safe and functional access throughout the project during the entire construction time period. Given the amount of time involved in pre-construction activities, a mixed use project does not readily lend itself to a bid process which commences at the completion of the design phase. Involvement of a general contractor during design seems to be the only practical approach.
Property managers/owners: Typically, a property manager for the entire project must be appointed, with clear powers and reporting responsibilities, and hopefully, there is a clear methodology set forth in the development documents as to sharing of costs, allocation of revenues (e.g.. parking) and decision making for the various areas, including budgets, landscaping, insurance, maintenance, etc. Individual components within the mixed use project may have their own property managers, and frankly, engaging separate property managers for this purpose might be warranted.