I'd like to thank you all for your inputs.
In addition to options 1 & 2 above, I have come up with option 3.
Option 3 = BOTH.
I will go ahead and use the fused and diode charge line that I already have installed. AND I will buy a 20 AMP Li battery, fabricate the input and output cables, and house all of it in a small plastic (Harbor Freight) toolbox for portability.
I find that I can build a more powerful battery power supply system that will do exactly what I want for slightly less than I paid for the Jump-Pack (which I have already returned).
Thanks again,
Tim