Well, I was only like half serious about that, but it isn't really such a far fetch theory. I don't live in Japan nor do I understand Japanese to be able to read Tanuki or any other sources that can be more factual but..
Take Taka from One Ok Rock as an example, even though he migrated from the Jpop industry (Johnny's Entertainment) of being an idol to being a JRocker, it is possible for VK artists themselves to think about migrating to Jpop/kpop/idol industry in general. (And also again, I don't know much about Kpop industry itself too but there have been more and more Japanese members in groups recently).
But, I would think Jpop is a little more lax with idol training than, in Korea. Japan's idols (that debut) is that you watch them grow from being meh to being good, like you're an inspirational shit because from shit to good/awesome you become. Whilst in Korea, to debut you have to be exceptionally good. These are talent-wise mind you and not face wise yet.
So let's say, in the VK industry older bands like Malice Mizer, Dir En Grey, X Japan, and Luna Sea are slowly starting to retire and let's admit it, they will sooner or later or else age will catch up to them. We have their predecessors like The Gazette, Alice Nine, and Nightmare. Bands that have been together for more than, 10 years but these people are also past their prime. 5 or so more years and they'll be like the first ones I mentioned. Where are their predecessors or roadies that became their kouhais? That they helped throughout?
Most of them have disbanded and some are leaving the scene. I would take examples of bands like Screw, SuG, ViViD, and Born (note most of these are under the PSC labels because I tended to focus on them mostly before I left the VK fandom for a while a couple of years ago)
Some of the members of those bands or other bands like them have left. Others are still continuing but, we're still seeing how they'll pull through.
Now, with that information at hand, added with recent dramas/crime allegations and real VK artists that have been jailed, we now have newbie younger artists that may want to be part of the VK industry but, would find it rather hard to do so as senpais and labels would be harder to find. Not to mention that they did say in the earlier posts that the vertical hierarchy has been slowly fading (Prob because the older artists are retiring and such whilst others are still trying to recover from their disbandments and are off worrying about how their new band will survive the industry). Although, there are label companies that are owned by VK artists as well, I'm not sure of delving into that topic yet as I haven't researched about it yet.
So with this in mind, there would be two ways a person can go with this.
1. If they're serious about their musician career in VK (like Anfiel maybe), it'd be harder with people flocking over the older bands because nostalgia and fear of them disbanding because of the recent trend of dissolutions from 2016-2017 or it'd be harder to make a name and find fans who will be into VK because of recent issues (like that Egoist and 12012 dudes killing their girlfriends or with the recent issue of Kisaki being a pedophile).
2. If they're not serious and are just in it for the money and sex, they would think its easier to migrate into the idol industry that has been gaining more and more attention the recent years. Not to mention, Jpop has been slowly catering to Kpop culture as well of aesthetics and face value, the only problem they would encounter there would be the strict dating rule, but then again many idols can get away with that if they try hard enough. (Also, I'm not saying being an idol is easier, because seriously the idol industry is more cut-throat that in the event you don't sell or don't have fans you will starve.) with VK you can have Mitsu's and Tsunagari's but, who's to say that idols can't have them too? Not sure, so will have to research further on that part.
That's my take/theory on VK boys migrating into the idol industry lol and seriously, they might as well try their luck whilst they're young. The moment you're 20 when it comes to their industry, it'd be a whole lot harder to debut since, they prefer younger ones and think 20 is too old already to be an idol debuting.
Please take this reply in only a very small tiny bit grain of salt cuz I just love making theories and shit about things and analzying things but, please remember that I do not live in Japan or Korea, nor do I understand/can read their languages lol