Question on eligibility - Derivative rights of residence

[webbynz]

Quick question all. Could you please tell me if our circumstances suggest that my non-EU wife could obtain a Derivative rights of residence permit?

I am a British Citizen living in Scotland, I own a house in Glasgow and I work as a full-time IT contractor
I have been married to a New Zealander, married 8 years ago
We have a Scotland-born son, 6 months old
My wife and son are in NZ after her spouse visa expired, we've applied for another but given I'm self-employed UKBA is making it as hard as possible to satisfy the financial requirement - so I thought I'd look for potential options
Our son needs his mother as she has been his primary carer his whole life

From what I've read the proving the primary carer bit might be the most difficult. Does anyone have a similar experience to mine? If not, does anyone know if our situation could mean that she can obtain this permit?

Thanks in advance
Ryan