CVI in CRM 7.0 and ECC 6.0 IS-A VMS

Question

Hi experts
I'm seeking for techinical advise on solution for CVI (Customer-Vendor Integration) in the given landscape.
Refering to an excellent article from Mitchell Faiman (SAP) in CRM Expert and SAP help for CRM 6.0, we've done all the needfuls to set up but still has some issues.
We're implementing a landscape with CRM 7.0, ECC 6.0 EhP4, NW EhP1, and IS-A-VMS (Vehicle Managmeent System). One of the key requirements is keeping BP master data clean and consistent across the landscape, including having the same ID, and having a mechanism to keep any changes reflected across the chain regardless of the change being made in CRM or ECC. In VMS, there is a requirement to have end-customer created as BP (role VLC001), as well as being a customer (KNA1) for SD Sales transaction and vendor (LFA1) for kickback payment in ECC. This is where we thought of CVI as the ideal solution. The ideal flow for us would be to have BP created in CRM (role CRM000), then via MW object BUPA_MAIN creates BP in ECC (hoping to find a way to default the role to VLC001 here as well, but that's another issue), and then with CVI, consequently creates a customer and vendor record, and extend ECC-BP with the FLCU00/FLCU01/FLVN00/FLVN01 in the process. (Flow diagram: CRM-BP -> ECC-BP -> ECC-KNA1 & ECC-LFA1)
Once I've gone through the setup as mentioned in the article and SAP Help, I then proceeded to create BP in CRM only to find an error in the outbound queue in CRM reporting a syntax error in ECC program SAPLSFP_CRM. It turns out that there is a missing structure in ECC table which has not been activated (Actual error message is "The data object ES_FKKVKP does not have a component called ZAHKOND_SC" . We found out that this structure is related to FI-CAX (that explains the use of function module FSL_BUPA_MAIN_INBOUND instead of COM_BUPA_MAIN_INBOUND in Faiman's article). 
The problem is, we simply cannot activate FI-CAX as that is considered another IS solution/business function, and according to SAP notes, only one IS solution can be activated per environment (we already have IS-A-VMS). That's a brick wall for us, and I wonder if there is anything we can do to overcome this.
Obviously I have created an OSS note to SAP and has been in touch with the support consultant, who have advised on the restriction as mentioned, but no further solution is recommended just yet.
A few questions here:
1) Can you validate our understanding of the CVI concept and the flow?
2) Will the slight change to the flow to rather create BP in ECC, then via CVI create KNA1 and LFA1, and consequently via MW object CUSTOMER_MAIN create BP in CRM work? If not, any solution to this at all?
I would appreciate your valuable feedback and a proper solution that solves our issue will be awarded with points (as always).
Thank you

Answer 1

Just an update.
SAP got back to me after a few dialogue to confirm that the function i was intending to use (CVI via FSL) is part of FI-CA, and is considered another IS function. However, since we already have IS-A installed (switched ON), it is not possible to activate such function in the same instance as the general rule from SAP is that no more than one IS is activated in one SAP instance.
I did not quite understand this restriction though, and wondering how automotive company who sells cars as well as act as a financial leasing company would live within the SAP environment.
We've resorted to enhancement solution (one-way activation), which is only half a solution we expect CVI & CRM MW should be able to offer.
Thread closed.