I suggest adding a function to iD and JOSM that would allow you to change the date, just like when you look at the map on OHM. In some places, several elements with different dates are superimposed, and it can be difficult to know whether an area has been mapped with the right dates (see example: OpenHistoricalMap).
This feature would make it possible to enter a date and see the chemis and polygons present for that date, which I think would be practical.
Can you take a look at those, make sure we’re headed in the right direction, and if you have any suggestions, add them on the ticket? More work has been done on the JOSM ticket, so I’d start there.