You are asking of course for more than can be delivered on a 'just an answer' basis. I've designed and built many skids over the years, the engineering required to create a *reliable hot water skid for use in a region with no technical back up goes way beyond finding a water heater with 70 liters per minute flow rate... many if not most of those include extensive electronic controls, that are prone to failure in rugged environments and then cannot be serviced in those environments.
Here are your options, at least when dealing with me here on Just Answer.
Its a premium service, and includes full engineering, vendor identification, cost/benefit analysis, complete set of CAD drawings, calculation sheets... and range of options.
First stage conceptual design services, which may or may not be sufficient for construction, but will include conceptual drawings and equipment specs, for several options.
Second stage includes complete CAD drawings of the option chosen so that the mechanical aspects of the skid package can be built from those drawings. $450
Third stage includes a range of electrical schematics and options, and the sales package you may need to present the offer to buyers, including 3D animated CAD graphics, drawing and slides package... with an eye toward dominating that market.
My background: Available here on Just Answer, with licensing etc verified, is 55 years in the industry including numerous mechanical skid packages, a hot water boiler skid, and the MX missile test stand cooling for Aerojet General Corp.
I am currently semi retired and working for a fifth of my previous rates as I travel, and do what can in other areas.
If you are interested let me know, or if you wish I can opt out to other of our experts here.