To be honest I don't see the problem on doing that, it just a artist working on more than one series. But there are artists in around the world making manga not just one but work on multiple stories at once, it a bitch to do so there shouldn't be any problems to do so. Plus the series have to be notice by the people who runs Webtoon, by the numbers you get on each series; such as the subscribers count and the page views count. You need a lot to be qualify of your worth in the Webtoon community, you can look up how much the numbers of each is worth in money. So just make your series with different accounts each is totally fine that just make them happy and get them a lot of money.