I'm certain tyre flex has been modeled from very early on it just hasn't been represented graphically - I'm sure your just trolling though :P.
Latest release talks about "- The tire model has an improved solver to find the amount of tread yaw under dynamic conditions (i.e. non-equilibrium). This has significantly improved transient behavior and tire response to changing loads."
which has the potential to change the feel a lot.
So if tread yaw is being modeled tyre flex would be pretty simple in comparison..
So instead of trying to mathematically solve things you have no sight on, how about getting to race or may even get a proper wheel to transmit the FFB from iRacing? The tires feel pretty neat finally and they aren't just lego blocks under your car that have some grip.
How do you define good enough? Countless championships in sim racing have been won with far inferior wheels than dfgt. For sim racing if you want sheer speed basically every wheel you can buy nowadays is good enough. But for realism you probably "need" a servomotor wheel like simsteering or accuforce wheels.
DFGT is fine. I've never had a problem with feeling the car in iRacing with it. The only bad thing about a DFGT is the pedals, the wheel itself is good. In iRacing you need a better feel on the brake pedal and can't just go 100% brake like you can in some other sims, that's the only reason I can think of you might struggle with a DFGT but I personally never had a problem
Exactly a point I mentioned in the General Discussion topic and how load-cell pedals act in LFS compared to other sims. Basically, you might say having a loadcell pedal in iRacing if you compete in a non-ABS car is heaven and hell.
I never had a DFGT, but I had a G25. It was enough to feel the car nicely around the track, and gave pretty nice inputs from the tires to not feel like I'm driving a LEGO car. I thought that was perfect. Then I got a CSW and it's not only a single step forward in FFB feel. But that's to be said in rF2, AC and basically anywhere except for LFS, which is weird.
... and I'm just sitting here with a bloody old momo with a loose worn axis, getting NO feeling through the wheel at all. Not to talk about the crap pedals that have almost no resistance and the throttle axis is cut at least 50%.