There is an 8-15mm L Fisheye in the bag (on the left side - just above the bottom corner) - also the 17-40 F4 L top right.
I have thought a lot about a fast very wide prime, and may do it, but so far the 35 1.4 and the 24-70 2.8 and the above 2 wide angle zooms seem to work. I also have the 35 F2 with IS that I use in certain situations and really like a lot.
A crop lens that I have, and that I wish was available in full frame, is the 18-35 1.8 Sigma. This is a lens that I would pay a serious amount of money for because I could shoot an entire wedding likely on that and the 70-200 IS.
In terms of flashes, I was sort of in the gear investment stage when the 600EX-rt was out and on sale ($400 not the $600 list) and decided after some experimentation that they worked well for me. I carry 2 triple flash brackets that I can very quickly rig up either a powerful off camera flash system if need with battery packs that work in full day sun with high speed sync, work on or off camera as bounce flash and are very easy to control either in manual mode, ettl mode, combo mode within the 5D3's menu system. From a reception perspective, again you can have lights in corners on small stands, attached high up hidden away with clamps with battery packs, and change everything from the camera or from an attached 600Ex-rt to give you focus assist in low light or from the ST-E3-rt Controller if required. I have also rigged up a Manfrotto 1005BAC stand with 2 C clamps that I can very quickly, if needed outdoors, attach 6 flashes, with gels if required as the flashes all have HONL velcro straps on them, that can directly into the sun at very high shutter speeds to blend the ambient and fill flash. I looked into Profoto B1s and their controller system but decided for now that what I have works for me. I did invest in 2 Wescott LED daylight balanced Ice-Lights which I think are great for very quick setups for indoor portraits or night time lighting - they only last just over 1hr so you really need two and or the battery pack (which I listed in the bag description as being under the 8-15mm L Fisheye zoom)
Hockey and wedding photographer. Favourite camera / lens combos: a 1DX II with a Tamron 45 1.8 VC, an A7Rii with a Canon 24-70F2.8L II, and a 5DSR with a Tamron 85 1.8 VC. Every lens I own I strongly recommend [Canon (35Lii, 100L Macro, 24-70F2.8ii, 70-200F2.8ii, 100-400Lii), Tamron (45 1.8, 85 1.8), Sigma 24-105]. If there are better lenses out there let me know because I haven't found them.