Trychnos,
I do not understand the structural "design criteria". call me wierd, but i have done many diffrent things under this heading.

1. Does this mean you will be providing input into a "design brief for structural components" for architectural, structural, civil and services for a D&C tender, aka say it is a processing plant are you to provide gather and report the expected heating and cool effects for concrete design ect?
2. Alternatively, is your input more complex like development on the architectural for building concept, ie slab thickness, column size and positions ect, aka processing plant again, to you help in the layout of the structure?
3. Alternatively is your input less complex, building a design criteria report like Woolworths throws out each time they do a development, mainly in relation for minimum specification.
For 1 & 3. Your liability would be minimal, generally, we would price this as an investigation and report, thus it would be man-hours x 2.5.
2. Your liability is medium, and your advice has to be such that an engineer in the future can take you preliminary design and develop it. Generally would try to do this as a $$$/HR, if not possible i would go for 0.5% of estimated total construction costs or man-hours x 5. I say your liability is medium because if you do not do it well and another firm rips your design up, you look bad, so good development is a high priority, and you can waste time here, lots of time.  

When in doubt, just take the next small step.
 

rowingengineer
Thank you for the information.  Based on current scope we fall between 1 and 3.  However, I'll probably include provisions in the proposal in case the scope expands to something like 2. At that point we can obtain additional compensation for the expanded scope.
Thank you for the information.  It was helpful.

Caring of future liabilities, I would state within the "design criteria" that the firm commissioned in the end with the design shall be responsible of meeting all and every of the specific legal and technical requirements in the scope of the commission that are not generally or specifically addressed in your "design criteria", which are, of course, also to be complied with. This way, you direct the way the works must be conducted yet who takes the money, takes the liability. In short, you give advice and guidelines to the development of the work (acting as complementary rules), useful and helpful to meet intent, but just that. Meeting the design intent is just the purpose of an engineering commission.

Thank you ishvaaag.  This is also helpful.

I may be overthinking this, but I question the Clients intent. Why did they go to you, the local specialized firm for design criteria only?

Is it to get your expertice for less fee and then hire a firm better connected (and controlled) with the Architect or the Client?

I would try very hard to find out why you can not have the total project even if bid in two phases. Your effort here may draw out the Client's motive. At least include some kind of monetary incentive for getting the total job after the first phase. ie: Markup the value of your expertise with a discount for full design and tell them so.

Good luck. Let us know the outcome.  

Thank you SteelyLee.  We will keep this in mind and look into it further.