So it sounds like it is not a "full reset" to those times, but basically level 75 and all old systems, except gear scaling and level synch, which would be included despite being more modern additions.

You would probably need to keep some of the level-specific casket-drop armors/weaps, and maybe a RoE-type NPC who sells lvl 1-75 basic armor/weaps. Because if everyone is xping and doing events on the old slowmode system, you aren't going to have enough people synthing and farming all the mats for making gear. Sure there will be some people fulltiming the synthesis lifestyle, but probably not enough to provide all the level-specific gear for a whole server.

The other problem I can see is people who have built RME past lvl 75 lol. Those people are not going to join your server, and lose all the work they did.

Its a nice idea though and I'm sure quite a few people would be interested.