Just a small bump for this and with a bit more specific request.
I have used the 'first person' mode to record and had great results. However it would be perfect and amazing if it was possible (and I realise it may not be possible) to get the hotbar and the inventory to show too. If this were an option I would 100% throw away OBS and simply record real time with Replay mod cutting to timelapses seamlessly and getting bullet time on skeleton fights.
Yeah that is sort of what I suspected tbh, however if there were a way of doing it (even if it doesn't integrate that well with the system) then consider every minecraft youtuber using RPMod for all their recordings. There is nothing that RPMod can't do that a bit of screen capture software can. Even integrate voice recording to sync with timeline. Just my thoughts on directions to become the industry standard.
Again I know that there is probably very hard limits on what you are able to do but I'd just keep it on the table is all :) thanks for the answer.