Hi, another member interested in a bluetooth gh60 here.
I've ordered a nRF52832 board to do some software and power consumption tests. I've never done pcb design before so I hope to get some help in that aspect.
Your board has an older nRF51 series chip, with somewhat worse power consumption.
Here are some of my thoughts on the topic:
Unless supply for a certain bluetooth module can be guaranteed, I think it's better to integrate the chip and antenna onto the main pcb.
Also, I think a single chip solution (with nRF52840) combining bluetooth and usb would be ideal, but the packaging on that chip is be a pain to deal with. A two chip design with a dedicated rf chip would probably be easier to layout, the downside being software upgrades becomes more complicated.
Regarding power consumption, the bluetooth chips from nordic semi claim to have an active power of around 6mA, so a current consumption goal of 10mA should be achievable. At that level, a even a small 600mA battery can potentially last more than a week (few hours a day of use).
I believe the cost for such a board can be brought down to around the same as a gh60 as well, considering how an atmega is actually slightly more expensive than a nRF52832 (cortex-m4 processor with integrated bluetooth, sadly no usb though).