Bizible established touchpoints based on campaign responses. The way I have set it up is by using Salesforce as the source of truth for campaigns responses and this has allowed me to identify (with a custom model) what working at TOFU, MOFU and BOFU. My best practice of generally having a 1:1 relationship between the Marketo Program (a specific webinar) and an SFDC campaign (for that specific webinar). I don't sync what was sent only registered, attended and no show. Bizible established touchpoint for the responses. Then you'd do this for all campaigns (by campaign type) across your channels to see multi-touch attribution.
I use DemandbaseOne (DB1) not 6Sense, but they are similar in concept. DB1 sees all of these campaign responses (leads & contacts) and aligns it to the Account so I get a centralized view of activity (leads and contacts) in the Account, and then I set my rules for defining MQAs. DB1 integrates into MKTO and SFDC, and 6Sense seems to be similar. I'd say look at Marketo and how you are pushing campaigns responses to SFDC (what Bizible established touchpoint on) and then map how 6Sense and your campaign responses help to create opportunities. We attach contacts to opportunities (to identify the buying team) and this helps us to see all things that contact responded to over time to help analyze impacts. I think this should help you to make that connection via SFDC.
Another option may be to write your 6Sense data (a campaign response basically) directly to an SFDC campaign with a specific campaign type and define it in your Bizible touchpoint set up. In your SFDC / MKTO instance your Marketo channel (tags) should have alignment with your SFDC campaign types to understand the impact of attribution. Hopefully this gives you some ideas on how you might make the connection between Bizible and 6Sense to create touchpoints that help you to see what campaigns/content are having the most impact in the touch before the opp is created.
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