I'm going to come across as a killjoy here, but it's my engineer brain running nonstop and some nasty personal experiences that are driving it.
I'm assuming the fat red and black cables tucked back by the wheel well are the battery cables. They should be protected, as should the battery.
Honda puts the battery in the back corner of the engine bay partially because it's a very survivable location (it's also easy to access, and close to the starter). The odds that area will be destroyed in a wreck are small (that corner is the junction of 4 frame members, more or less), and the odds the battery will short and/or explode are smaller.
Putting a battery in the trunk does a similar thing. It's in a more deformable crumple zone, but placed in the spare well or near a shock tower it's highly survivable, and poses similar short and explosion risk.
Putting the battery behind the bumper is, IMO, stupid. It's an area that sees high vibration due to it's relative distance from the CG of the car. Batteries don't like to be shaken, even the 'special' ones. It places it in a hugely risky position. Catch a high curb? Battery shorts to the frame. Tap a catch barrier? Battery shorts to the frame, or splits open. Catch the corner of another car? Battery shorts to the frame, or splits open.
Do me at least one favor, ok? Put a properly sized fuse as close to the positive terminal as you can. Like really close. Maybe bolted to the positive terminal. Then make sure the battery top is covered by a doubled layer of 1/8" rubber, to mitigate contact with the steel above it. I've seen batteries go. Two of them have sent me to the hospital. One exploded and burned me, through my cotton clothes. One shorted and vented sulfuric acid into the air thick enough I had some chemical burns in my lungs. Neither one was subject to the violence imparted in an accident, or the additional risks that are carried by such a location as yours.
As an electrical engineer, batteries don't scare me. Neither does AC power. Or high voltage. Or high power RF (think of your microwave). That doesn't mean I'm not wary of the dangers. A battery, whether it be lead-acid, lithium, or some other novel chemistry not used in automotive applications, is a very small step away from being a bomb. Care and feeding is what keeps it happy, and not explody. Lithium needs even more care. They don't fail happily at high temperature like lead-acid batteries (kinda) do. And if you puncture one, instead of leaking like lead-acid (usually does), they have a habit of causing very hot, very nasty fires (and that's just a phone battery).
If you want any more support for my position, look at the rules for sanctioning bodies in professional motorsports. None of them put a battery in a crash zone like that.
Those are all very great points that you stated, and most of them have already been taken into consideration. Where I failed in my prior post was a detailed explanation on what specifically is being done with the battery as precautions.
Before I do, let me reiterate that this vehicle sees very little mileage in a given calendar year. In 2014, the vehicle saw 10 miles total. In 2013, 412 miles were put on the odometer, and 2012 saw 318. The purpose of the vehicle has always been a "weekend" or "sunny day" vehicle, where excessive road time is null, along with being a show vehicle. Not that accidents can't happen during those times, but the overall chance of an accident occurring (IMO) is slim to none.
This year, there will be one racing event in October, in which I'll be attending. It's held twice per year, but I've already missed the scheduled event this past July. I don't anticipate any accidents or failures (not to say that they can't happen), but I feel that the battery placement currently will be suffice, overall.
Precautions so far, will include rubber boots on both the positive & negative battery terminals, as well as a 200 amp fuse on the positive terminal. My goal is to have it bolted directly to the terminal (as you suggested), but it will be dependent on which direction the cables will be routed. As long as room allows, I don't see why it can't be bolted to my battery terminal clamp.
As much as I know that there are better locations suited for my battery, I stop and think about my 1990 Ford Ranger, and my 1991 Honda Accord that have the battery directly behind the passenger headlight. I realize that the battery is above the front bumper supports in these vehicles (where mine is below the support), I can't help but think that no matter what accident is involved, the battery in any of these vehicles would take a great hit, no matter how many precautions are applied. Even if the battery was installed in the trunk, a side impact would more than likely, shred the 10-12ft cable, and the same result would occur.
In any case accidents can occur at anytime, and I hopefully never have to find out if this idea is a good one, or not.