Hmmm.. I was under the impression that 88's attached to Wehrmacht were for use in the AT role. Be that as it may, even if dual role, Guderian's XIXth Motorized Army Corps had 3 batteries of Luftwaffe 88's attached as well as a company of the portee version.
Looking at the parent organization (Gruppe von Kleist), there was one battery of attached Luftwaffe 88's per division basically. For comparison, there was a platoon of self propelled 47mm ATGs per division. In Gruppe von Kleist, there were at least as many attached Luftwaffe 88's as JPz I's.
Slicing down to the typical battalion level for the game, using Gruppe von Kleist as a model gives about half an 88 or a bit less than half a JPz I per battalion, so yeah uncommon in one way but not any less common than other typically used units.
Confusingly, at Arras, the 88's Rommel employed probably came from PzAbwAbt 525 which was a Werhmacht unit with 88mm FlaK guns *not* a Luftwaffe attachment although there were also Luftwaffe 88's attached to his parent organization
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Another part of the picture I'm missing is the number of towed 4.7cm ATGs available. From the data I've been looking at it seems the towed ATG battalions of Panzer divisions in 1940 may have had some but most infantry divisions had only 3.7cm ATGs. I'm not sure if it would be something like one platoon of 4.7cm ATGs per towed ATG company in a Panzer division or ???
I guess the suprising part of this is that the JPz I's were as rare as the 88's.
Brian