Finance issue – under contract

Hi Everyone,
We've run into an unexpected hurdle. My partner started a new job 5 months ago (prior to that he was employed in one job for 9 years) and is under a 6 month probation period. We didn't really think about that at all and didn't know that it affected finance. We have our first investment property (have a home in partner's name with a fair bit of equity that we are using) under contract – settlement 2 days before my partner's probation is up.

I've talked to our mortgage broker and I am able to finance the property by myself – but we wanted joint names so that we could share the tax deductions. The main reason we want this is so that in 5 years time when we have kids and my wage decreases i can still manage to earn enough to claim the deductions but it won't be so hard since partner's wage will only go up.

I don't get this – if i can service the house myself – why do they care about my partner – doesn't it only make it better having it over catered for with his income as well?

to keep it in both names could we have a guarantor? and then remove the guarantor 2 days into the loan when partner's probation is up?

also i'm worried that if we have to change it to my name that would mean a new contract in which case the sellers might choose to ask for more bids – they've had a lot of interest in the open homes since we signed the contract.

our first option is talking to my partner's employer and trying to get them to drop the probation – his boss is fine with this as they really like him – but it will be up to the HR people.

Any advice would be greatly appreciated.
Thanks