The tunnel vision on merging all the regular servers into one server on this forum is astounding to me. Especially when it comes from people who likely haven't played the game for an extended period of time and that think "maplestory is a massively multiplayer online game" is reason alone to merge all the regular servers.
The only concern you seem to have is population. Other concerns that would drastically affect quality of life in their proposed server, like crowding, lag/stability, and bots are thrown to the wayside, despite being legitimate concerns in for the server you want.
In regards to population, there's already two "big" servers for you to choose from: Reboot and Bera. Reboot already holds half the GMS population and is the most active server. It's also known for being difficult to find training spots in, and having stability issues. A world that results from merging all four regular servers would have a population on par with reboot. That would, in turn, also have it suffer the same problems as reboot. Bera's considered the largest regular server, and even it gets complaints regarding overcrowding and stability. If Bera was to merge with the other regular servers, those lssues would certainly get even worse. Yes, a low population in a server may not be a good thing. But some players would prefer to be in a less populated, more tight-knit server. A high population may actually turn some people away. Interacting with a lot of people can be overbearing. A low populated server would be preferable to those.
Another issue regarding population is crowding. As I've mentioned before, Reboot and Bera are both notorious for overcrowding. Finding grinding spots in either world is difficult, Reboot especially. A world consisting of all four regular servers would make finding training spots nigh-impossible. This would be a major QoL decrease for players and would deter them from playing the game. Especially during 2x events, when the servers become particularly busy. More channels could be added, but that's only a band-aid fix to the issue. More channels and only hold so many more players/maps. And Nexon is very unlikely to provide more channels to your proposed server. Even then, more channels won't do much to alleviate issues of lag.
Lag is a major concern for your propsed server. Reboot and Bera are known for lag. What makes you think your merge server won't? Better yet, if Elysium, the proportionally smallest server, somehow manages to lag, why wouldn't your proposed server lag?
Finally, merging all the regular servers into one would further concentrate the bot populations of those servers into one mass. That would definitely be bad for the game health and player experience. Channels would be more likely to crash. Meso prices would skyrocket.
All of these are reasons why a world merge wouldn't be healthy for the game, and shouldn't be implemented.
As for a world transfer, face the reality: After the disaster of the last world transfer event, it's likely they'll never happen again. Even one did happen, Bera would likely be blocked off to prevent polarizing the world populations again.
Also, as a person in a "dead" server: stop speaking for me. I, and several others, chose to stay in my dead server. I don't want people who haven't played Maplestory in a prolonged period of time to decide what's best for me, and neither do most of the players outside this forum.
TL;DR - Stop asking for a world merge. You don't speak for everyone and clearly don't understand the consequences of merging half the GMS population into one server.