I think it would be really useful to add player designated map markers so you can mark important locations on the map like entrances to caves and meeting points. They should also be team specific. People normally end up making markers with colored blocks anyway.

Yes in my games people always build coloured arrows and tell people to attack. It would be a lot better with markers.

Don't let people draw on the map, people will just draw cocks.

I think the whole point that we can make our own shit on the map is better than any implemented feature. You want to draw attention to something? Draw it on the map. Someone drawing a cock shouldn't hamper your playing experience.