From what I've recently read, virus don't always mutate to be weaker, that seems a massive, massive misconception, which I used to believe too, and I've posted saying I thought that too (I was wrong apparently).
But onto what this could be/ do:
Faster spreading but slightly weaker is extremely bad news for those with poor vaccine uptake or limited supply.
Faster spreading but able to avoid vaccine antibodies is extremely bad news for those with good vaccine uptake, but limited infection.
Faster spreading but able to partially avoid a mix of vaccine and infection antibodies is a big unknown with good vaccine uptake, and boosters, but having a lot of infection in the community over the passed 2 years. We're in this category, but the problem for us is a lot of our most at risk are just vaccinated, but have had limited natural exposure (this has been a good thing though).
In any case, people with boosters would probably fare well if the HAD to face Omicron, but those with two/three vax and exposure to infection probably the best of all.
Antibodies aren't the be all and end all though, there are other things like T cells etc etc.
I think if I had to chose, now (which I don't), I would chose double vax, booster, and then get Delta (assuming I've not already been exposed, which is doubtful) before Omicron takes over, which is possibly around Feb.
This is not in any way a suggestion for people to go out and get Delta mind, especially without being double/ tripled jabbed, I'm young (ish) and have been in many situations where I've already probably been exposed many times. The at-risk are best off getting triple jabbed and then trying to avoid everything until an adapted vaccine becomes available, or until specific healthcare advice changes, or until we know a lot more (very early days).
This below was quite worrying mind, albeit doesn't consider boosters or other protective measures/ body response: