I think you're over complicating things... just do your 90 day reports on line, even a duffer like me managed it in 2 mins . then do your extension as and when they're due. No advantage in aligning them.
Also, and this is Office specific, the IO may well process your 90 day report for you agin when you complete your extension (Phuket Office)
Can't you do your 90 day report on line? I did mine online yesterday. Took 5 mins. When you do your extension in November ask if the immigration officer can combine the two. It's not really a big deal deal.