I would:
a) configure that router manually as you need/want it to come up after a re-flash (so all WiFi set-up, and passwords)
b) make a copy of /etc/config/wireless (and any other config files you like to "inherit")
c) copy these to ${OPENWRT_BUILD_ROOT}/files/etc/config (replace OPENWRT_BUILD_ROOT with where you built openwrt, not the "outer" openwrt directory, but the first one with multiple sub directories)
d) build a new firmware
This new firmware will use all files found in the files "hierarchy" a very convenient way to customize your own OpenWrt builts, but it will require building your own...
The image builder has an option FILES where you can specify a folder with custom files to include. Just copy there your custom file /etc/config/wireless with wifi enable. You can also setup SSID and password and your wifi will be immediatly operationnal.
will it work ** uci set wireless.radio0.disabled='0' uci set wireless.radio1.disabled='0'**
i just want my device to have wifi on after reset so i can set up over wifi
Are you intending to flash OpenWRT to a device for the first time? Or are you intending to upgrade a device that is already running OpenWRT to a new version?
If it's the latter then as long as you select to keep the current settings and configuration (which is the default option if upgrading through Luci) everything will be kept as it was before the upgrade, including how the wifi was set up.
Doesn't answer the question. Are you intending to flash this build onto a device that either doesn't have OpenWRT or where you've opted to not retain the existing settings/configuration during flashing, i.e. doing a 'factory reset'. Or are you intending to flash it onto an already configured and working OpenWRT device where you'll be keeping the settings and configuration?
If it's the latter then you don't need to do anything to bring wifi up after the reflash. If it was on before you flashed it'll be on afterwards.
If it's the former then you'll want to add some additional commands to set SSID and, presumably, some security. Running uci show wireless on a configured device will show the relevant uci settings. You also need commit wireless at the end.
If you are flashing over a pre-existing install of OpenWRT and are not getting rid of the existing settings then you don't need to have anything in the uci-defaults. The wifi will come up just as it was before you flashed the new image.
But yes, the commands you've added should turn the wifi on.