First of all OLIMEX has grate products. Is In Bulgaria next to my country Greece.
Actually we are disusing with Olimex to use the A20 CPU board (But with T2 processor for industrial and automotive use) to build an HMI for our CODESYS runing PLCs.
After testing it I wanted to run OPENPLC on that board if possible. So I may have an HMI user panel and a PLC in the same package.
That is the idea and I am waiting from Olimex to have T2 board ready may be this month.
We are going to get these parts from Olimex ASAP.
Now considering the AllWINER A13 it is indeed a powerful chip but the design is not going to be easy. Thinks can go wrong with noise and the hole design can be unstable. Olimex has the board ready if we want to have a try but it is a board that will not have the acceptance of a raspberry zero and they have similar prices. Zero motherboard is nearly ready. We have to develop a new motherboard for that . Olimex A13 board is about 77x42 mm (if that can fit inside motherboard).
My opinion is to go for the T2 CPU module from Olimex (A20 CPU pin compatible but all board is extensive temperature range) and adapt it somehow to our system.
55 Euro for that board is a grate value for money. We may only have to do some kind of different motherboard and connect it to our system.
That can be done the "next day " If I may say.
And the best thing is that Olimex designed it in KICAD. (like the laptop they are selling)