In cross compilation builds, the current TH situation is a bit of a showstopper. However, much TH code is 'safe' to cross-compile. Before the TH situation is solved, it would be great if GHC could automate as much of the work-around process as possible. -dth-dec-file is a big step on the way to create a non-TH version of the source. However, there are some problems with the generated code. One is that qualified names from hidden modules are used. A instance declaration for Aeson.ToJSON is outputted as follows:

instance Data.Aeson.Types.Class.ToJSON InputDropboxFiles where

Ideally, GHC would be able to combine the splice output with the original file, replacing all $() with the corresponding splice, and even generate correct imports. I personally think this would be a great solution to the TH problem. Most cross-compilation projects could just generate the non-TH version with the host GHC, and the few that depends on architecture specific variables can be edited before cross-compiled