so let say i have 3 access point with access list that specify minimum range of -60

scenario; one goes down, let say a reboot was needed
how to allow clients to connect to other one with a bad/slower connection (having the 2 other active one reducing the limit to let say -70) until it goes up again?

only way i can think of it creating a netwatch script that ping AP and change status of access list based on the response
is there any other (better) way?

On the clients you can use the connect-list and set your priorities...
https://wiki.mikrotik.com/wiki/Manual:I ... nnect_List