Without GPUs, i feel like this will take too long and people would lose interest. Really need to get this working with GPUs instead of CPUs. We really need to decide on a number, say 0.0001% of possible keyspace or something, and see how many collisions are found. We could extrapolate that number to the rest of the available keyspace and determine how feasible and attack would i.e. how much money would need to be spent, what type of equipment, etc.
I think we'll find that it's very infeasible, but I (and presumably you) could not find any actual data on this which is why it makes it interesting!
As for this code being dangerous, i mean i guess, but a quick search on Google shows that tools for hacking loaded keys already exist for free (Hashbasher is shared on this forum) and I haven't heard of anyone ever having coins taken from cold storage. However, if someone did win the cosmic lottery then it would be difficult to prevent them from taking the coins. I have never heard of a cold wallet being drained so I think the chances of this are similar to the chances of finding a collision in the first place.