Im suspecting that this will not be for a Part 135 but rather for a Part 91K operator? Or rather flying under Part 91 with the owner and their invited guests?
In which case the strictor of the two sets of regulations apply, the Russian or the FAA.
Quick search came up with this but I'm not sure it applies: FAR 23.807
If Russian regulations are somewhat similar to EASA I would suspect you CAN NOT use a kit built experimental for Commercial operations regardless of emergency exits.