as if 90 days were enough
Tell me what do you need 90 days for?
When it comes to PCC, you can submit your application without those that have long time to get, as long as you add your LOE with the explanation that you have applied and either you were rejected to get one, you need a special document from CIC to get one or the delivery time is too long (greetings FBI). Then you can submit your PCC as soon as you will get it.
Now for the other documents:
IELTS / TEF - you should already have
ECA - you should already have
Proof of fund - takes just few days to get
Proof of work experience - all previous work you can get before ITA (since you left those jobs, as long as your proofs are after you have finished that job - the reference letter, you are good to go). And as for your current job, you should be able to get it within 2-3 weeks.
Birth certificates - this can be done and get ready before ITA (for children), again once issued they do not age
Translation services for the listed above - 2 to 3 weeks for all that
Medical - within 1 month max (yes it might be that some are overcrowded, but you can choose any of those in any country as they are registered with CIC). if a woman is pregnant, you can still submit incomplete medicals (no xray for chest) and once the baby is born you will have it completed.
I guess what they have found out that maybe 90% of all applications were sent within those 60 days anyway. So this way they will know a little bit more exact who is just letting their ITA expire.