It's primarily because of this that I'm against 2017-03:
1. It will not serve to improve IPv6 deployment
My memory is that the original /8 policy was implemented, not to encourage/discourage IPv6 adoption among existing IPv4 holders, but because we recognised that new entrants joining the internet, even when IPv6 capable throughout, still require at least a little bit of IPv4. Best I can tell, that's still the case.
So we're neutral on getting existing holders to shift, but I think this proposal is highly positive on the number of new entrants who'll be able to take this path.
2. It may go as far as to seriously impact the size of the DFZ
I don't want to dismiss the impact that RIR policies have on the DFZ (it's why we started making them, after all) but the DFZ ultimately operates on its own (very raw) consensus. Fragmented blocks do work today, down to /24 - and we have no idea how full runout will change the dynamics of already-routed blocks.
So if fragmentation of the remaining /22s in the RIPE free pool may have a serious impact, then I'd suggest that we need to prepare for fragmentation, whether or not this policy is adopted.
Of course, RIR policies do have an impact - but only for as long as the policies remain meaningful. Once the free pool is out, and fragmentation of existing blocks becomes the sole way to get more addresses, there's not much more we can do on this mailing list to affect the DFZ.
3. I see no benefit over the current policy
So in summary: the original last /8 was meant to get new entrants onto IPv6 by providing them a little bit of IPv4. I'd like this to continue for longer.