Loosing income support as a carer.

I have a couple who claim IS on the grounds that the wife is a carer for her husband.  He was awarded DLA under special rules several years ago when he was in a critical condition in hospital.  His Macmillan nurse made the claim and assisted the wife in making the IS and CA claims.  He is now much improved and his DLA care has been reduced to low rate.  Wife has 8 week run on of CA but has been told she needs to claim JSA from mid July.  Her husband is not really fit for work but if he makes a claim for ESA (ir) they will loose their disability premium and have only personal allowance for 13 weeks.  Even if he passes the LCW test he will still have less money than if they make a joint claim for JSA as they would keep the DP.
If he had made the original IS claim on grounds of disability, they would eventually have been transferred to ESA without loosing out financially.  Is there any possibility that main claimant could be swapped over before IS ends?  Has anyone come across any similar cases?  It seems very unfair that a couple can be better off looking for work than incapacitated.
Be grateful for any advice