On movement speed - Certain maps it is certainly fairly griefy to die 3-8 seconds into the round while still buying nades. Locking movement at the beginning of the round, however, is not imo the way to address it. Using your mic +teamwork and/or countering with a certain race seems much more reasonable.
On new players - There aren't enough SO's to be instructing every new player 24/7 on how the server works. As Toad stated about instructional messages that is an excellent idea. I understand we already have wcs / war3menu but the fact of the matter is this is not 1.6 / source and the community of GO is not as patient, understanding or familiar with community servers. Should wcs be enough? Yes. Unfortunately many people leave before even scratching the surface of the information they need to take in. My suggestion, on top of reinforcing Toads idea, is to appoint those who wish to assist in the matter to a "helper" position. No powers such as kick or ban or money but just be able to talk in colour chat and stand out as an official to help new players get in their groove. I remember when I first joined a warcraft server in source I read forever until I understood because 8 year old me got screamed at, called a retard / goof / etc. Most people leave after someone says "READ WCS YOU IDIOT, GAWD PEOPLE ARE SO STUPID"