Using non ECC vendor

I have client request that they won't create the ECC vendor master record until the bidder has been awarded a contract in SRM.  We are using Extended Classic Scenario without PI, is following doable or any recommendation:

1.      Supplier self register through Ros
2.      Buyer accepts and create local vendor in SRM (different # range from ECC vendor)
3.      When a local vendor becomes “winner” of the contract/PO, manual creation in ECC for vendor master (this should be ext. # range, using the same # in SRM)
4.      Vendor replication from ECC -> SRM (update) – we need to test if this works ?
5.      Create PO/Contract in SRM then push to ECC

Thx,

Wendy