I'm pretty sure the airbag light will come on if you disconnect it and then turn the car on. Is there a work around? Maybe I don;t know but there should be plenty of threads where guys are running after market steering wheels and the answer should be in one of them.
keep in mind that removing one air bag disables the whole SRS system (all air bags), hence the warning light on the dash.
in my hondas, i've had success installing a common resistor in the wiring to trick the system into thinking the air bag is still there. this continues to enable the passenger side airbag to still function in case of a collision (plus no warning light). it is unknown to me if a similar solution can applied for lexus cars.
as for cruise control, it depends on the adapting hub which will need to retain the clock wiring. then you have to figure out a way to retrofit the stalk on the hub/wheel since the on-off switch is on the stalk itself. i have not seen it done yet.