Spitoon, that has to be the most disingenuous remark ("a simple controller")...
Although I am trying to persuade other posters - with a degree of subtlety, I hope - that reliance on IR W/V on short finals, in preference to ATC surface W/V reports, is generally NOT A GOOD IDEA; it's their accuracy and relevance that seem to me to be the problem, not their currency.
(1) IR HDG has to be instantaneous; most modern airliners do not possess flux valves, their only magnetic heading sensor being the ubiquitous E2B standby compass (or derivative of). IR HDG(T) is converted to HDG(M) by applying the local Variation. [The IRU knows where it is, and has a world map of Isogonals.]
(2) ADC TAS, being IAS-derived, is instantaneous AND not of declining accuracy.
(3) IR TRK is instantaneous for all practical purposes. How would the FMC know when to roll out of a turn otherwise?
(4) IR GS is also instantaneous; the platform constantly knowing the number and magnitude of accelerations it has experienced since last alignement.
Items (3) and (4) are, I believe, the weakest links. They are instantaneous, but their accuracy declines as a function of time since last IRU alignement. The latter can only be performed when the aircraft is stationary.
The relevance of an IR W/V reading at 100 ft agl on a night approach, accurate or otherwise, is another matter...