Assuming it's been kept up regularly, even a pan drain and refill with a new filter *should* be good enough. That's all I'm able to do in my CLK430 (aside from a full exchange monkeying with the cooler lines) as it has no torque converter drain, and apparently it was enough to make MBZ happy with 39k fluid/filter changes after they decided the "filled for life" stuff was utter nonsense.

If I did have a torque converter drain, as I do on the W124, I'd certainly do it, but I tend to do the fluid and filter every 25-30k ahead of the MB-recommended interval to keep things working fine. It tends to still look pretty clean each service, even only getting what's in the pan and installing a new Mann filter, but it did have its first service with 4134 ATF at about 35k, so that could have something to do with it as well.

If it had 100k+ by the time I first serviced it, then I'd probably look at doing what you are doing. That's actually how Honda themselves recommend servicing neglected (and ultra-delicate) autos in their cars, IIRC it returns about 86% new fluid in those.

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1995 E300 Diesel
~300k