Maybe not (really) related to FIA R4, but this one relates to AP4, another alternative to R5, and this made me surprised.
There are some rumours in Indonesian rallying that one - estabilshed - rally teams are designing Mitsubishi Xpander AP4, which the base comes from the MPV car itself.
Previously they planned to build Mazda 2 AP4 after their visit to Australia/NZ, but it didn't happen because their ties with Mitsubishi

Cmon. Nothing isn’t decided
[WRC] Vodafone Rally de Portugal...