@Rod Stewart posted:How about this instead Stan:
Is that a statement or a question? 
So here's my 2021 take on the "situation." As of late, I'd say the most common recommendations on OGR for isolated-rail triggering using a relay are (1) Z-stuff DZ-1008, (2) Azatrax MRAPR, and (3) GRJ/Hennings ITSD:
After shipping and what not, we're talking at least $15 and up. To each his own as to how thick one's wallet is, and if these off-the-shelf options represent adequate value. I always like to point out how even Lionel sold a relay board, the 153E. I think it might qualify as a collector's item today!
So to throw a "new" design into the mix I'd think it should bring something new to the party. I agree your board should allow one to save a few bucks if willing to do the leg-work (accumulating parts, ordering bare PCBs, soldering, testing, etc.).
What if the "problem" is posed as how cheaply can one make an insulated-rail relay module for signaling, crossing gates, and the like? In other words, eliminate the word "universal" or the notion of one-size-fits-all.
Remember this is a discussion forum for the exchange of ideas. 
That said, here's a different tack. The starting point are 12V DC relays for 50 cents in small quantity.
The different tack is to ask how cheaply/simply could one turn this 50 cent DC relay into an AC relay that operates at 14V AC Accessory voltage. Again, the idea is to remove the "universal" concept and go for the "silent majority" of OGR users!
I say adding 2 generic 1N400x type diodes might be all that's needed...along with screw-terminal blocks if desired. I'm wondering whether you could then make a 14V AC relay module for around $1 ... or in any case less than $2 in small quantity.
Again, the idea is to keep it simple with a minimal number of unique parts.
In fact, if you have some of those HK19 DC relays and some generic diodes lying around I can elaborate on my thinking. I don't know what your target price is/was on your relay board. My thinking is simple: to attract the "typical" OGR reader to fire up the soldering iron (if they even have one!) you need to present a stunning value proposition...rather than just saving a dollar or two.
My 2 cents of course. 
