I don't think you need to retire the cooler MLT for this. I still use mine and don't see these problems.
The graphs from the experiment are a little misleading when it comes to the achievable efficiency. Yes, conversion will happen faster at higher temps, but higher temps are not necessarily necessary for full conversion. I explained that here:
Understanding Efficiency - German Brewing Techniques
The idea is that there should be enough enzymatic power in the mash that you can reach a point of saturation (where no more or only little starches are left for conversion) This point will be reached earlier with a higher temp than with a lower temp, b/c the a-amylase works quicker at higher temps. But that may not matter if both temperatures reach this point before 60 min. You may also extend the time of the rest if using a rest temp below 150F. But to reach this point of saturation, the other mash parameter will have to be optimal enough.
While mashing at 145 and then at 160 for full conversion is exactly what German brewers do, you need to keep in mind that if there is a significant gain of conversion efficiency at 160F, it will be in the form of poorly fermentable extract and lowers your attenuation potential. But for a typical German beer with 80% attenuation a 30-45 min mash at 63C and then 30 min at 70C works well (at least for me).
WRT to the maximum temp of the mash for lautering, I have found (in the literature) that the limit of 170-180 is not set by the sudden extraction of tannins, but by the desire to keep the a amylase active during lautering active as it is needed to convert any rouge starches that are released during this process. I know this goes against the widely accepted knowledge that mash-out kills *all* enzymes, but this makes more sense to me and I have also shown that a mash-out does not kill all enzymes. There have been some heated debates on this on the NB forum.
Longer mash times and higher mash temps increase the tannin extraction, but there is not a sudden jump at 180F. It's more about the pH then the temperature.
Kai