Take an old automobile diesel engine and mount it on a small trailer. Mount dual alternators, a hydraulic pump, and an air compressor on the engine. The dual alternators would provide 24 volts, which would allow it to be used to recharge the battery bank in an off-grid power system. They could also be used to provide power for electric arc welding. The hydraulic pump could be used to drive a wood splitter. Compressed air has any number of uses. This would be just the thing for off-grid DIY home builders.