Any mains-powered Z-Wave device (i.e., not battery-powered) will act as a repeater/extender. However, keep in mind that Z-Wave locks are ‘beaming’ devices and to be effective for the lock, the Z-Wave extender you choose, also needs to be a ‘beaming’ device. (See here for more details)
HOWEVER, if the yellow light next to the ‘A’ button on your Kwikset indicates that the motherboard is bad - as was reported by Kwikset, adding Z-Wave extenders will not likely be of much use.
Also, replacing your lock with a WiFi lock might not be the best choice either. YMMV, but generally, WiFi devices have terrible battery life because they’re always on rather than Z-Wave or Zigbee’s more ‘sleepy’ protocols. Besides, the issue with the Kwikset locks isn’t that it’s Z-Wave. To be blunt, it’s because it’s a Kwikset with poor design and/or implementation of their motherboards or modules, or both.