Hi Jeff,
You are absolutely right. The IDX and IDX Pro is missing those features you mentioned. However, the recovery time of these machines seems even faster than an MXT, making them outstanding in high trash areas. And, an MXT does not have a volume control either unless you want to change the sensitivity at the same time.
It was those IDX and IDX Pro shortcomings you mentioned that caused me to suggest an XL Pro as an alternate backup choice in an earlier post. The XL Pro has an analog meter instead of a digital readout. The numbers on the XL Pro meter face correspond fairly closely to the VDI numbers from an MXT. Like an MXT, an XL Pro will indicate very accurate coin depths when using the stock coil. When properly adjusted an XL Pro will search very deep. An XL Pro operates at 6.59 kHz making it a bit more sensitive to higher conductive targets than an MXT. An XL Pro will not only be a good backup for an MXT, it has features that will compliment the performance of an MXT.
I own and use all 4 of the models mentioned in this post.
Good luck and have fun, Bob