Have we ruled out simple substitution unwisely?

[Koen G]

Again, I encourage you to play around with this to get a feel for what works and what doesn't. Whatever you do at a given location in a word (in this case [in]-clusters at the end), will still result in severe positional constraints. You'd also have to randomly pick how to parse any given [in]-cluster. This can be simulated easily by sectioning your corpus, processing each part in a different way, then putting them back together.