The TSP I Fund is perfect if you want to invest in Japanese and Western European markets. The issue I have with the I Fund which I expressed in my writeup on the fund is that there are a lot of other investing opportunities overseas in other areas.
The upcoming change to the index tracked by the I Fund will give it a broader reach, but will make it trickier for me to decide when to invest in it (it will combine developed and emerging markets). My preference would be to have more than one international fund in the TSP, but it is still a good step as the new I Fund will include faster growing economies.
The “Look Forward at 2018” post explained why I believed the I Fund in its current form is a good investment right now.