Design PCB: modular SSR boards and isolated sensor boards for DIN rail mount

I need to design several boards using cadsoft Eagle. All of them have to fit in some DIN rail mounting or box. I have an idea that all boards are designed for any custom length / module count (up to some logical limit, like 16 or limited by DIN rail box length). This way I could make board of any length or cut already made board into several pieces. All modules should have LED's for indication. SSR board control input signals and input isolation board output signals should be compatible with TTL levels and npn open collector (pull-up resistor will be soldered on board), rated for 5V. Boards have to have wire to board connectors with screw or a spring (if price is ok). Two inputs on one side, two outputs - on another on each module. SMT components preferred except for connectors. Even through-hole S26MD02 may be soldered as SMD. All boards should be compact, simple to assemble, no un-needed components. 0805 size SMDs used. Single sided is better, because I may want to make them at local lab. I will need Eagle sch and brd files and files for production at [login to view URL] or similar. 1. board with SSR relays like S26MD02 or triacs for loads, including inductive ones like industrial solenoids. I think S26MD02 will be capable to power number of solenoids, because my solenoids have power rating of 12VA and holding power rating of 9VA, 230V AC. The requirement is to power up to 4 such solenoids through one SSR. 2. board with SSR relays or triacs to be capable of controlling up to 3kW three phase 400V AC motor. Input channels should be separate. 3. board for digital sensor power and isolation. Sensors will have common power: 6-36V DC, but I can stick to some voltage like 6V or 12V or 24V if needed. Sensors are NPN, open collector. Isolated board outputs: open collector, 5V. I want you to make engineering calculations and write them for me in very simple form, elect components, look at their prices, ratings, etc., I will give sources where I can buy from or I will help to compare prices. All schematics should be given for confirmation before PCB design.