I thought about creating a shader with relief mapping...

It should be possible but I'm not sure how to implement it into a custom shader for shade-c.
Are there any information about the #defines (especially the custom vs and ps), so how do they
work and what do the input- / output-structs include?

also I'd like to know if the depth for the deferred lighting's gBuffer is calculated
in the object shader or with a second VIEW*.

If it's done in the object shader it should be easy to manipulate it based on the relief-mapping's
depth result which makes it possible to use SSAO for the displaced texture

EDIT: ...and the shadowing would be correct, too.
(except for self-shadowing, which can be done in the object shader)