Well, one of the big problems with "spin-gravity" is the Coriolis Effect.
To be honest, I don't intuitively understand the Coriolis Effect, and I haven't read up on it. But I just "kinda" know the following about it:
1) The Coriolis Effect is sufficiently significant to generate atmospheric spin, and weather/circulation patterns across the entire planet Earth!
2) When you have a small object spinning, such as the BFR, The Coriolis Effect will induce slight force-differentials across different parts of your body. Though slight, these differentials are enough to cause rather severe nausea and a VERY intense feeling of "sea sickness".
We don't have a lot of experience with spinning up space-craft in space, which is pretty astonishing to me, considering we've been playing around in low-earth orbit for half a century now!
You would think that in 50 years NASA or Russia would have conducted a few major experiments in spinning craft... but they didn't... not really anything significant.
If they had... then we would likely now know exactly what to do with the BFR mission astronauts to Mars, to simulate Mars-gravity all the way there.
But now it will be up to the private sector to conduct these experiments.
One option might be to tie 2 BFR's together with a long tether (or some sort of counter-weight) and then spin them, so they both rotate around the center (in the middle point of the tether).
AND FINALLY...
Some think that if you want to truly avoid the Coriolis Vomit Effects... and make space travel very pleasant, then you might have to go big.
Really big!
Big, like this space-port-station discussed in a recent episode on Isaac Arthur's channel.