Programming the chip should not be too much of a concern.
you can create a board with ZIF,zero insertion force socket
surface mount units are available if you want to use a surface mount chip.
the board would have all the needed USB connector and a switch to turn off the power, let you swap chips, then put in the next one.
as a note, you take some nail polish and put a dot on the chip. colored dots = version.
but that is on the programming side.
also, if you want, I believe you can send your sketch to DigiKey and they will program the lot for you.
if you plan to make your own PCB, you might consider JLCPCB and their EASYeda.
you can use the parts from their sister company when you add a part, it automatically gets added to the BOM,
if you use all parts from them, it can also make your order form.
in some cases you have to order a minimum of parts, like 5 or 10, when you only want one.
the cost from JLCPCB is so low that you can order 5 boards, and parts, build it, test it, change it and order 5 more.
as a note, you might want to add gold pads in places for test points.
also, if your design a full surface mount board, with the common parts from JLCPCB, they will solder the board for you. since it is fully automated, they don't do the thru-hole.