There are lots of variables but I'd say it would be reasonable for the NRP to have the DC for 2 weeks in the summer hols with the EOW also still being in place as standard. However, the RP should be flexible as to which two weeks those are, and whether they're taken as a block or as two separate weeks, as they don't work and the NRP will have to work within their company's holiday availability.
It would also be a factor to consider how much holiday the NRP can take during the summer holidays as when you factor in other times of year (Christmas, Easter, half terms etc) plus any holiday they might take without their DC (eg a week abroad with a new partner; time off to attend a friend's wedding at the other end of the country etc) then much more than a couple of weeks often isn't practical, especially if the RP isn't working and is available.
It will also depend on how old the DC are as older children are going to have a lot more independence and can be left to their own devices more. So while NRP might have DC for a week, unless they're going away for a holiday, then it's perfectly reasonable for them to leave a 15yo DC to their own devices for a couple of days while they're at work whereas if DC are 5 then they can't do that.
ExDH and I share custody 50/50 and that normally means DD spends every other week with each of us, however in the school holidays we tend to rejig things so DD spends longer blocks with each of us so that we can go on holiday and so it's easier work wise.
Because we both work we try to be flexible around each other so one year we might have DD for a straight 3 weeks each; the next it's alternating 2 weeks each and whichever parent only has 2 weeks with DD will have her longer over another holiday eg Easter; the year after is 1 week with me, 2 weeks with ExDH; 2 weeks with me; 1 week with ExDH etc.
The key to that is that we have a really good co-parenting relationship so we are happy to help each other out as and when so if the relationship is not a good one this might not work. Eg if we had agreed to have DD for 3 weeks straight each, I went on holiday with DD for 2 weeks but in the 3rd week I had plans one evening then, as long as ExDH was free, he would be happy to have DD for that night even though it was "my" week and wouldn't expect me to do the same on his time just to "keep it fair".