Congrats!
I’ve yet to actually introduce mines I think

Maybe we could do a rp with all our ocs as like a big chat room?
But for ocs

If everyone agree of course

Wait what exactly do you need permission for, you say?

I'm not sure what an rp chatroom would be like since I don't know that a lot of characters have phones here (maybe they do idk) and I doubt they'd have each other as contacts, but maybe you're imagining it in a different way than I am.
Anyways, ofc you're free to do whatever you like, but I would suggest making a thread with a party/event or a strange happening to intro your character. Try to think of something in which other people's characters characters might be interested and want to investigate or join. It's kind of the thing I'm used to, lol. Maybe it's too classic-y. 

Yeah, like Specter said, the GGaD forum is probably more used to the premise they described. Rather than being from various dimensions, it's more common for different characters to frequent different Sects (Medieval, Modern, and Cyber), and from what I recall, characters from all the different Sects usually only congregate in weird occasions. For instance, when the WoFMB closed, I remember a bunch of characters coming together in threads to say goodbyes. 
...but congregating together in the same place in the same Sect isn't all that logical either (that's what usually happens lol), so if you describe the setting, I'd say go for it. That is, as long as the roleplayers participating get the relevance (future implications) of the thread and are okay with it, I don't see a problem with it.
If I may offer a bit of advice, though, it's that bringing together a bunch of characters who usually occupy different settings and do different things might have long-term consequences. For instance, canonicity is a thing, and different RPers weigh that differently. Another example is, how much does it really make sense for so and so to be meeting so and so, and how will that reflect in the future? Some character relationships are more meaningful if they're not forcibly brought together in large numbers.
Of course, the roleplay has been a bit dead, so I think this could also be a great opportunity for some characters to branch out or just to do things. Just putting some things to consider if you would like. 
No matter what, I hope you all will have fun!

-Galaxian-