She doesn’t have to have citizenship to apply for benefits if needed and yes she will be able to work .
It’s not hard to renew visas .
My Thai wife came here in 2003 on a spouse visa , got a job on an agency after one month and after 18 months when we divorced she got legal aid free of charge and a good divorce settlement.
You are very much mistaken my friend . He has married her through the British embassy and when she comes to the U.K. on the marriage / spouse visa it will be his responsibility to support her , she will be able to work and will have the same rights as any British woman .