Hi Aleksi,
I can see one snag, if IPv6 assignments from other RIRs were accepted: multi-national corporations would hoard "an automatic /22" from every RIR slightly more easily than the current policy allows. In that case I would also add policy text that would make sure that if the applicant already has a final /8 IPv4 assignment from some other RIR, they can't get one from RIPE.
I have to point out that making our own policy dependent on policies in other regions is a dangerous thing to do. As Elvis has already pointed out not all regions have a final /8 policy. Lat's use ARIN as an example: They have adopted proposal 2008-5 (https://www.arin.net/policy/proposals/2008_5.html) called 'Dedicated IPv4 block to facilitate IPv6 deployment'. This is a needs-based policy where someone can get between a /28 and a /24 for e.g. dual-stack DNS servers, NAT64 etc. ARIN also has a waiting list for IPv4 requests (https://www.arin.net/policy/proposals/2010_1.html), and a policy that returned IPv4 address space will be re-distributed as quickly as possible (https://www.arin.net/policy/proposals/2011_6.html). If you go down this road, exactly which address blocks an organisation gets from ARIN will prohibit them from getting a /22 from RIPE NCC? And if you look at organisational structure it becomes even more complicated: what if a big corporation has subsidiaries in both the US and EU, and the US company gets address space from ARIN. Does that disqualify the EU company/LIR from getting address space? Remember: someone has to be able to implement the policies we create here! :) Cheers, Sander