This is simply not feasible. MSI can only pull the data of 1 Marketo record. And a Marketo record can only be sync'ed be sync'ed with 1 SFDC record (lead or contact). The best you can expect it to be able to create multiple leads in SFDC, but either they will also be duplicates in Marketo and each of them will get a portion of the MSI activities, or you can hide some on the duplicate from Marketo with a Sync filter or some restrictive sharing rules, but in this case only the sync'ed record in SFDC will get the MSI info.
May I comment on one thing about the process: having the same person been called multiple times by different sales person from the same company in a short period of time because they have shown multiple product interest is really a non customer-friendly way of doing business and a sure way to exasperate your prospects... I see many companies that are pushing their organizations issues down their customer interactions process while claiming to be customer centric.
The most efficient organizations are turning towards a model where the various interaction are logged against the lead, and the sales rep in charge of the first qualification will have the responsibility to determine which of these product interest can really lead to some business and which are mere curiosity.
We discovered that we can accomplish this by having MSI write to the lead only if there is no contact and to the contact pushing to all leads created off that contact. By doing this we can create a contact person if there are multiple leads for 1 person and then the MSI writing to the contact is copied, all data to the leads off that contact person