I think the NRP should be the one paying the fee if they hold up or obstruct the system not the RP who needs the frigging money.
Plenty of RP don't have £100 lying around because the NRP is being a dick in the first place which is why they have to go through the CSA rather than working it out amicably in the first place. They can ill afford a % cut on a pittance most of the time anyway. Are the new CSA really going to take a % off the £5 that is all they enforce from some?
As such I think some will be so lacking in morale (spelling) and thinking why bother that they won't. Is is really going to be worth all the hassle, stress, abuse sometimes from NRP PLUS the cost of £100 + % for that £260 a year (52 x £5) You may just get your fee back 
Same staff.
Same staff with too much workload or time to do anything effective most of the time.
Same not chasing hard enough if someone doesn't reply because they can't possibly be there rather than just ignoring the letters.
Plus there will still be ways around it such as presenting 3/6 months low pay slips to show a new income, taking the rest after a rate is agreed and then boosting their pay. The RP disagreeing and it all going round and round in circles.
Would be useful if they are going to be given some real teeth to deal with evaders but based on the governments opinion that single parents (read mothers) are the scum of society and to blame for all it's ills I don't see that happening.