I am in favor of standardizing on the Go codebase for pluggable transports that ship with Tor. This is something we talked about at the last developer meeting. The reason I favor this is not for reproducible build reasons, but because maintaining four implementations (C, Python, C++, and Go) is confusing for PT developers. As far as I know, since the last developer meeting all Tor products have been migrating towards shipping the Go PT implementation so that they can get obfs4 support. Last I checked, some of Tor products are also shipping other PT implementations in order to maintain access to transports not available in Go. I imagine that there is some time in the future where there will no longer be any bridges available for the older transports and so bundling clients for them will no longer be necessary. However, I don't know what the current level of use for non-Go transports is. I'd love to know if someone has those stats.
I also don't know how well reproducible builds work with Go, so if someone knows that would be interesting information.