Spark 2.8.3 Build 960 Configuration Question - Group Only?

I have a very specific need. Can this tool (Or is there another) which I use in a group of about 25 users for 1 to 1 communication and occasionally group and broadcast mode, be configured to NOT allow 1 to 1 communication?
I have issues of 1 to 1 communication being detrimental to the business and would prefer for business communication to be allowed only to the current logged in people in a group where everyone can see it.

You can try to achieve that with Packet Filter plugin. Create a rule blocking Message packets from any to any. I think it should block messaging between users in general, but should still allow to chat in MUC (group chats). There are some drawbacks though. This plugin hasn’t been updated in many years, i noticed that login in Spark is longer when it is in use.

An alternative approach is to provide access to a client that exposes a group chat only, something similar to what we’re providing for our own group chat at https://www.igniterealtime.org/support/group_chat.jsp

It would be technically possible for people to have one-on-one chats, but unless they’re very XMPP-savvy, they won’t know. An approach like that is not something you should take if (security) policies are in play, but for regular inter-office chat, it might suffice.