I don't really mind M60. But It's like 90% of the medics I meet, do use them. Bit weak to be honest, seeing as it is rather overpowered, comparing to the rest of the LMG's. But I guess they want some easy kills. Instead of going the extra length and try out any other LMG.
The MG36 doesn't have an iron sight, it has a reddot sight by default. So you can use any other specialisation like ammo upgrade, light weight, grenade upgrade or the medkit heal+
I either use the MG36 or MG 3 LMG when I do play medic.
The 40MM grenade launcher doesn't bother me. Until my killcam tells me, he's sitting with a couple of ammo kits by his side and with the extra grenade upgrade specialisation just tubeing away.
o/