Best backup suggestion for the Sony a9 (A7R or A7RII)

I'm a Canon shooter transitioning to Sony. I shoot high end corporate events, weddings, general portraiture, and also shoot some models. Most of my Canon gear sold off faster than I thought it would, and I never shoot without a backup camera. I don't just want a backup though, I want a camera that can compliment my Sony a9.

I don't necessarily just want a backup camera that gets no use. The a9 has a lot of strengths, but a large MP complimentary camera would be nice too when I don't need the fast AF (portraits, etc.) I was thinking obviously the a7RII is the obvious choice, but I've already spent close to $10K on the switch so that's a bit pricey right now.

So my question is, should I:
1) Hold onto my 5D Mark III and few lenses I have left as my "just in case" backup, and wait for a few months until the a7RIII (or whatever) is announced and a7R / RII prices drop

2) Sell the remaining Canon gear, and find a cheap A7R and buy that as a backup / complimentary camera now, because the IQ is similar in quality to the a7RII

EDIT: My Sony gear so far is the a9, Sony / Zeiss 35mm f2.8, 24-70 2.8 GM, and 70-200 2.8 GM

I'd get the a7rII Jared. I did the 5DIII and Sony thing for a while and splitting lenses across two systems gets old real fast. You also have to consider things like compatibility of lighting equipment between systems.

The a7rII is the perfect compliment to the a9 as cover each others weaknesses. It's a little on the slow side, but good enough for weddings and events and the resolution and DR come in handy when the time calls for that. AF on the a7r is not cut-out for event use IMO. High ISO performance is not so great on the a7r either. If you want to take a cheap route, snag an a7II, as it performs very similarly to the a7rII. (no af-c eye focus though).

I just ordered the a9 and feel a little sick to my stomach because of the cost, but really feel that between the a7rII and a9 I'm equipped to shoot just about anything and won't need another body for a long while.