Warm up

I don’t use D&T as a physical warm-up.
I consider D&T an energetic and spiritual organizer.
Each morning I do a lot of standard stretching and warm-up exercises which includes myofascial rolling, then quad, hamstring, calf, back muscle stretches.
When first learning Bagua I was careful to follow Bruce’s regimen, especially to loosen the fascia around the spine and organs.
But recently I have been starting my Bagua in the morning with no specific warm-ups (do not do this at home).
I only do a qigong routine called the Shanghai Hospital
Exercise (just standing and swinging arms like a pendulum forward and backwards). I study the I-Ching diagrams of the 8 directions while doing this.
I can immediately follow this by circle walking with no further specific exercises. Circle walking is not like playing football or other aerobic contact activities.
(Clearly competition or push-hands requires physical warm-ups).
This keeps me busy from 5 to 8 in the morning.
I no longer do the 3 Swings regularly or the micro-cosmic orbit qigong or Marriage of Heaven & Earth or other qigong routines).
Please don’t do as I say.
I’m just saying that soon you may develop your own personal routine without a prescribed warm-up.
If you practice with sincerity you’ll slowly progress.

And thinking about warm-ups even more,
do Bruce’s warm-ups assiduously.

I may short-cut them because I’ve done them for years and I also do a lot of other warm-up exercises.

But spinal/sacrum safety is paramount.
Each morning I also do a yoga sacrum alignment set.

Doing D&T would not be a safe substitute for Bagua specific warm-ups which work on twisting leg/torso fascia.

Complimentary Yes.
Substitute No.

I’d say do the warm ups. They’re tailor made for bagua.
In fact, I think the dizziness that you posted about in D&T might also be if you are using it as a warm up for bagua.