Telemetry system with Arduino Mega 2560 and/or Raspberry Pi 3 B+

We need to develop a telemetry system using arduino mega 2560 and/or raspberry pi 3 b+.
The inputs for the system will be various sensors (digital, analog, hybrid, etc).
The output will be delivered localy (equipmend with screen), maintanance handheld equipmend (customized fabricated monitor with display or smartphone/ipad)  and remotely to web page (partial working: http://welotech.net/admin/home).


Each output module shall be capable of showing selective parameter, in general the local monitor should show the most important parameters, the maintenance handheld much more that will assist in problem solving and repairing, while the web page monitoring shall be capable of creating more complex data (sensors data readings with formula proccessing) and stats monitoring.
Connection to handheld will either cable or wifi, and to webpage by wifi, ethernet or gsm module (if not internet provided)

what needed to be fabricated
1) the main blog diagram with all connections
2) a schematic plan with detailed parts and connections in a way that will be easy to fabricate to full project from the scratch
3) the handheld monitor equipment proposal plan
4) the local monitor equipment proposal plan
5) a) the software needed for running the web page with all data that have to be stored and visualized by certain formulas. The visualization should have the ability to the admin user to enter a formula, select which data to use and select how they will appear (gauge, clock, bar, graph, line, etc) and where on the screen.
  B) The end user will just log and see what they are allowed by the admin.
  C) There is also need for app to run in smart phone for the end user.