Why are Remote Offers not supported in the VEC. The only options available when using the "Replace Content" feature of the VEC are "HTML Offer" or "Experience Fragment". I believe that in the past Remote Offers were supported by the VEC, but now they are only supported by the form-based editor.
Unfortunately they have not been available to use in the Virtual Experience Composer. This is because they are created and hosted somewhere else and also because they should use a custom mbox location (Not target-global-mbox) they are not supported in the Virtual Experience Composer. This has been documented in this Knowledge Base article: Create remote offers I know this is not the answer you were hoping for however I do appreciate your understanding.
Mihnea Docea | Technical Support Rep, Customer Care | Customer & Employee Experience | Adobe | (:: 1 (800) 497-0335