Assuming you are UK based.
Just a few words of warning for your plan:-
There is a 4 month sleep regression. Its hell, and lasts a good few weeks and, frankly, is like torture some days. I'd not want to combine that and even part time work
Mat Leave (aside from KIT days) Has to be taken in one block. You can't do a half mat leave/ half work situation. You can drop in up to 10 KIT days without it affecting your Mat Leave.
There is no legal obligation on your part to notify your employer of how long you intend to take off. It is also illegal for them to demand a return date. Employers must work on the assumption you intend to take the full 12 months leave available to you.
You then notify your employer no later than 8 weeks before your intended return date. So if you are post baby and intend to return at 24 weeks, you must notify them by 16 weeks.
Cover for someone half in and half out would be a nightmare - by taking mat leave in a block they can recruit the right person to plug the gap.
You cannot underestimate how much recovery time you may need. Physically and mentally. It would be unwise to make any rigid plans before the baby is here and you are settled into life with a newborn.
Your dp/dh can also make use of shared parental leave, which you could plan after the baby is here. He can take whatever is left of your 12 month entitlement himself to extend time off where a parent is with the baby. Your mat pay doesn't apply to him. He would need to refer to his own Employers policy on that.
You may find it difficult to nail down childcare with such a quick turnaround. Childminders and nurseries often are full and holding waitlists.
You do not, and I cannot stress this enough, owe your employer anything outwith of your maternity entitlement. You will do yourself no favours bending over backwards for them. Instead, you should make plans that suit you, your baby, and your family. It is sensible to wait until baby is here before you start to look at your return to work.
With regards being contactable during maternity leave, do not make any promises to them that you will log on, or be available at all during your maternity leave. Reach out to them after baby has arrived to discuss KIT days and return to work.
I'm not saying in the above that you should take the full year, or you should not. Just that you shouldn't agree to anything with them until after the baby is home and you are settled.