Any gabbai who insists on people davening exactly according to halacha will end up being the chazzan about 85% percent of the time, and gritting his teeth for (almost all of) the other 15%…
Perhaps you can improve the situation somewhat by getting people to learn the halachos of tefillah. I think you are best off focusing on the most important issues (such as kavod hatefillah, amein yesoma/chatufa and other cut and dried halachic issues) before even mentioning things like fast vs slow songs (which, after all, is a matter of taste – us pure Litvaks prefer to sing Hallel to the tune of Eicha :).