Hi All,
Immersion suits are not designed as outerwear. They are unwieldy and difficult to put on since you’ve got to basically be able to step into them, zip them up, and pull both the hood up and the shield over your lower face. This takes a little bit of time, and once they’re on, you have all the mobility of Gumby. You simply cannot move fast once you have them on, and you’re not going to be donning them after the fact if you fall through the ice. The intregal gloves provided for hand protection on the Imperial are not all that great for grasping as they're really set up to keep your fingers warm.
They definitely can be used by emergency personnel to go after those that have fallen in (better choices now available)or, in my case, when a boat decides it doesn’t want to float anymore, and you have the time to put them on. I’ve owned an Imperial Immersion Suit since the mid- 80’s with an ACR Mini-B EPIRB, VHF handheld radio, flares, ACR-strobe, and dye markers all nicely packaged up in the various pockets. I usually try to don it once a year to check it out and also to remind myself just how long it actually takes to put it on.
The Stearns i580 Anti-Exposure suit that Bob V. mentioned is the only way to go if you’ve decided to follow that route in regards to ice fishing. Many years ago, I worked on scallop draggers during cold weather months to get my tonnage up for licensing purposes. Besides layering up under my Grundens, that option was the only one that worked if you had to move about.
Oil rig workers, tug, barge, research crews, and CG personnel use this throughout the cold weather months as it performs quite handily as an insulated garment with floatation capability. It is considered a legitimate floatation device by the CG- Class V.

Bill