Depends if it's necessary for the role or not really. If they are putting that in as one of the criteria but it's really not required, then it might be worth raising it.
If they were saying "this is a suitable alternative for you and therefore we are not going to pay you redundancy because you have to take this role" then your personal circumstances would have to come into account in deciding whether it's genuinely suitable and you'd be able to reject it as being suitable and claim redundancy.
But if it's just a vacancy that you can choose to apply for and flexibility is genuinely a requirement then I can't see a lot of grounds for complaint.
Ask if there is any possibility of keeping your current hours in this new role. If there is, great, apply. If they say no, then you say in that case you do not consider this to be a "suitable alternative" for you because of the significant change in working hours and you will therefore not be applying.
You also say if they have any other roles which would be a suitable alternative to your redundant role, then you are keen to stay etc etc, however as your own role is redundant, if there is no suitable alternative, you would like them to confirm your redundancy.