There is nothing special about bbPress members. To make a member list you can simple use any normal WordPress plugin or tutorial that does this, it will be the same.
Who’s Online widgets typically have performance problems, even the BuddyPress one which is why you shouldn’t really show more than a handful of users. It just doesn’t scale terribly well with the schema we have available (eg WordPress).
PM functionality won’t be coming to bbPress, sorry. If you need PM functionality you will probably want to use BuddyPress anyways.
It sounds like you should probably just install BuddyPress as it will give you all this functionality. These items are purposely left out of bbPress – to keep it lean and mean – and are made available in BuddyPress.