The problem I forsee is that if I have to keep calling in sick for her and bringing her home on her bad days she will eventually loose her job anyway... .Its a real dilemma... .She works in sales and I live in fear that the stress of an awkward customer could force her to do something silly... .
Your wifes workplace is not her rescuer either. they will not understand nor will they cut much slack if it is affecting their bottom line.
Odds are your prediction will come true regardless of what you do. If you get involved she will see it as betrayal and the consequences for you will be worse no matter how well intentioned. Many pwBPD struggle to hold down jobs, that is all part and parcel of the disorder.
Even you can finance your lives in a way that her holding down a job is a bonus, not an essential, it will reduce the strain.