E4s never had DTs.
What did have DTs was the E-7. Some E-7s were refitted in the field with rounded canopies (replacements to damaged squared-canopy sets) and some lost the nosecone point or had their pointed prop hub replaced with an open one (also replacement parts in the field) but the only Emil with DTs was the E-7.
I would love the E-7 (especially the E7 trop). Anybody know when they started using the 90-round drums for the MG/FFm? I'm sure it must have been around the time of the E-7s' long career.
Extra range, extra ammo, extra horsepower... It'd be a nice addition IMO.
But not for the E-4. I'm also no expert on if the SpitVb ever carried a tank [Edit: Our early 1941 SpitVb, that is... Not the later models many of which shared the same name but were not the same plane], but I recall previous comments that "basically it didn't" when this came up before.
IMO stop-gaps are what we used to have in AH (multiple variants in 1 flight model, combined K-4s and G-10s, etc) and it leads to messy arguments with impacts felt 10 years later. I think that's the wrong way to go now that AH is finally rectifying that sort of thing.