The question was closed by 5 members of the community rather than a moderator. I can't speak for them but I will speculate as to why. Perhaps one of them may chime in with their thoughts as well.
What sort of platforms are available to develop this sort of game?
This part of your question isn't very constructive. You offer a lot of good information about your specific case however what will happen is that people will just start posting their favorite game development platform. This won't help anybody determine what you should do.
So any suggestions would be greatly appreciated.
That is far too broad. We tend to look for focused and answerable questions.
I think I need to establish the architecture first before proceeding with this project.
This should be a given.
My suggestion to you is to try and focus on an aspect of the architecture that you are having trouble with specifically, and post a design specific question regarding this, or perhaps edit your post to focus it on a single area. When you have done this, flag it for moderator attention and they can consider it to be reopened at that point.
Also, in the future, please do not cross post the same question across StackExchange sites. If you posted the question in the wrong place, then flag it for moderator attention and they will take care of migrating it for you.