We initially planned for a close gap but things happened so we ended up with a 3yr7mth gap and its great! DS is toilet trained, self-plays, he communicates well and has a level of understanding about when i need to spend time with 3mth old DD. DS is now in kindy 5days/fortnight so i get 1-1 time with DD and time out from both when he's at school and DD asleep. IF we went again I'd like to aim for a 3-4yr gap again.
I've enjoyed my time with DS getting to know him and raise him on his own before DD and with DS now at school i'm looking forward to having the same time with DD getting to know her and lay the foundations down for a great child.
I feel that each of my children are their own person wholly and completely and i don't expect or want them to be the same or do the same things.
OP: your reasons for wanting a big age gap are good; i think you already know the answer to your question