A current topic is that of the nature of a circle/ring in regards to items. I have a idea that doesn't quite fit over there so here it is here.
An illusion created by Creo Imag, of a perfect circle/ring, would be enchanted in a item. This way a magus always has the ring he needs.
The question I suppose, barring the one of what defines a boundary of the ring being broken, in such matters, you could make this ring any size and oddly on any surface. This would alleviate many headaches as far as drawing the circle goes. It would of course still be limited to the magus actually tracing the circle/ring but it seems if the circle is there already, then the tough part is already done.
Can an illusion of a ring be a physical component of a spell? Would it require Vim at all, considering the nature of magic...
Using the CrIm to create a circle, which you than trace to generate a Ring/Circle for spellcasting, is certainly OK.
When generating the Ring/Circle, the "magus may use magic to do so, but that magic must not have a range greater than Touch, and the magus must physically trace out the ring". So the illusionary ring would either be just a pattern to follow when tracing, or would have to be created by the magus while physically tracing it out.
"Physically breaking" the illusionary ring IMO needs some troupe consideration: magically changing or dispelling it should do, but just stepping onto it might as well.
Our troupe has not reached a consensus on what counts as "breaking" a circle.
In this instance if we go with the idea that simply transgressing the circle, which seems the most traditional custom magic wise, then there is no issue. However if the troupe goes with a circle can be crossed unless barred specifically by the magic, then a illusionary circle would seem almost ideal in a lot of ways. You cannot accidentally erase it. It can't fade until the magic is dispelled. Lots of benefits.
Granted with a bit of counter magic or might power, the magic could be subject to dispelling, so perhaps the risks balance.