I mean things like placing emphasis on rate of fire instead of individual soldier accuracy and the research and development that went into creating semi-auto rifles/conversions such as the Pedersen device and the various French attempts.
I'm really interested in this topic, but unfortunately I haven't been able to find any good books concerning the prototypes/changing ideas of small arms in WWI. I'm also interested in how the SMGs developed, so if anyone knows about that, it would be interesting the hear about!
While I can't give you all the answers, I've done a little digging on Light and Medium Machine Guns in World War One.
Reliability and sustained use were very important factors, and when a machine gun from WWI comes to mind, we generally imagine either the Vicker's or Maxim machine guns, both sported very robust cooling systems despite their sluggish cyclic rates (~500-600 effective).
Combat was often static and extremely protracted, and the heavy barrel and thick water jacket on most machine guns of the day allowed these weapons to be fired continuously with a fair amount of consistency.