Let's just allow all guns in events that way what you earned from the "events" can be used in the "events". The more you "earn" (event coins wise) the better gun you use in events.
Ex: Yogy is getting chem this week, but I have an electric staff, he saved longer than me so he should be able to use it.)
Or ONLY event items allowed in events. That would be a toggle staff can use every now and then.