Merging 2 instances of Project Server 2010 into one instance

Right now I am working on merging of 2 instances of Project Server 2010 into single one.
2 departments started PS2010 trials independently; were running it for about 6 month and performed number of customizations:

• customer fields (project and task level). Some fields have matching name and different meaning / values and some fields have different name but same purpose
• different EPTs
• different Project Site templates (that's the most easiest problem to solve)
• one is using Single Entry, second one is using Free Form for progress reporting and no time sheets.

Beside custom fields, the biggest challenge is that both instances have over 50 projects that are actively being used and so far it looks that this will be the most time consuming operation.

Proposed strategy is to pick one instance that is more "clean" and less "messy" and have it as "master" instance and merge another instance into this one.

So approach will look like:

1. Backup instances
2. Pick one instance as master (I1).
3. Export project site template from I2
4. Import site template into I1
5. Unify custom fields
6. Try applying Playbook from I1 and then from I2 into 3rd instance to see the conflicts, rename fields /lookups in I2 if required. If not working out - move it manually
7. Export project from I2 as will be described below
8. Import projects as described above
9. Have PMs to edit new projects to have same project ECF values as in old system (This can be automated with FluentPro's ECF Migrator tool)
10. Copy resource pool from I2 via Project Pro into I1
11. Import resources
12. Replace resources in project 
13. export project sites from I2 with STS-ADM
14. import project sites into I2
15. Point projects into new sites
16. Verify everything :-)

The easiest workaround for moving projects between instances is to save all task level custom fields into standard local column (Text1..., Number1...) using Copy-Paste of columns, save a local copy, upload to destination server and copy values back to Enterprise custom fields.

I will update this post if will find one missing steps.

Update: We've developed a product - FluentBooks that allows configuration migration, merge and documenting. You can learn more here or watch a sample video in another our blogpost.