Some of the GI brass will need neck turned, some of it won't, I found when going down to 6.5.  The steel is uber hardened, through and through if you ask me, not like a US Krag at all.  I would think that should one fail with a higher pressure cartridge, it would not do so catastrophically, but be manifest in a cracked front lug, or by cracking where the guide rib bears, if that's properly set up.  I will write the pros and cons down.  One thing I thought about is although the Niemiller is .1 shorter to the shoulder, the pitch of the barrel threads is not .1".  So if I cut the extractor slot now, indexing might be a problem if I later decide to go with the Niemiller.