Spell's being cast won't be an option. There is a skill for that. If you work constantly with a team then you know what spell they will cast, or you know the words or indications what spell is being cast.

Regarding agreeing to show, this is a party thing, if you dont want numbers shown to otehrs in your party, then maybe you shouldnt be in their party <shrug> but might go wih the coding of percentages anyway. The big thing is how much of a mud hit it is, with low numbers everything seems feasable, but we get back up to 40 players and suddenly things can bog down.