Assuming that for some reason that defining a formal strategy is not possible, I would offer that you utilize a “checklist” containing the artifacts and information you require and socialize the checklist with the entire team and applicable stakeholders. The checklist should contain every document type, every piece of information, every decision and essentially anything and everything that you have ever and could ever need as part of integration. Organize the checklist in something of an ideal order of and even if delivery of items listed may be performed in parallel. When annotating the artifacts/information required for a particular due diligence project, do so involving and collaborating with key stakeholders and team members to create the feel of defining the needed items together. Defining requirements together helps to create a feeling of ownership and feelings of a jointly requirements. If done properly, your checklist of artifacts and info (not activities as this is not a project schedule) will in fact create something of a formal process to be followed and that may well suffice for lack of a perceived formal strategy.
At the same time, you should come to the table with templates and formats that may be used and are certain to meet your objectives. I’d also offer that when discussing and setting checklist requirement that you be willing to accept deliverables in their format is they meet your needs.
Hope this helps. If anything isn’t clear, I’d be happy to elaborate or even have a discussion.