I meant all "A" UTXOs --> D, all B --> E, all C --> F doing this by several transaction for every address from A BC set so that initial UTXOs would not mix ABC. Then you can gradually consolidate UTXOs on DEF set either by moving fund to new addresses or using some of UTXOs for the payment needs.
That's better, but it's still not great. Once you've moved from A, B, and C, to D, E, and F, if you then start to consolidate D, E, and F together, although a third party couldn't definitively link A, B, and C as all belonging to you, they could get a pretty good idea which they may be able to combine with other information.
If it were me, I would either pass D, E, and F, individually through ChipMixer or a coinjoin before consolidating them at a later date, or keep them separate altogether and just use them for various payments as you suggest.