HE111s have a greater payload than the 88s. Also, the original format being preserved had the 88s subbing for "some" He111s. More 111s, less bombers in the air. The 3 prior runs of this event had the first 2 runs nearly dead even, with wins for the Allied the first time by a single building, and the Axis the second time by a few buildings, then a rather large victory by the Axis the third time. Sticking with formulas that have proven to work. There is more than enough ordinance to take the buildings down to complete the objectives.
The typical bombload for a He111 was no more than 2000 kg during BOB. In AH we get:
32x 50kg
8x 250kg
2x500kg + 853L
1x 1000kg + 835L
2x 1000kg
1x 1800kg
That's all under 2000kg. The Ju88 on the other hand can carry:
10 or 20x 50kg
2 or 4 250kg
2 or 4 500kg
for a total combination of 3000kg of both internal and external.
Note, however, that the 500kg externals were pretty rare on the Ju88. Most BOB-era Ju88s could ONLY carry 2 external bombs (most often 250kg, but they were pushing weights to use 500kg as well), due to limits on the airframes, limits on the structure, limits even on the landing gear to hold the weight, the engines to take off with that weight.
If you want to limit the amount of ord, LESS Ju-88s is what you want. Also, I would suggest using the CM commands to prohibit the 4x500kg and the 4x250kg external options. Those are very much post-BOB loadouts on our post-BOB A-4 subvariant. They were used against Soviet Russia and used extensively... Just not in the BOB. Many BOB-era Ju88s had to load only half the internal 50kg bombs as well, so that they could load an extra fuel cell into the other bomb bay. That also would restrict the possible loadouts if you wanted to prohibit it with the CM codes as well.
Not to mention the fact that it's a good 20+ mph faster than the BOB-era bombers, carries 50% more ord, and has 50% more defensive firepower than the BOB-era Ju88A-1s that were available. I'd say that putting more He111s is far better to the scenario balance than putting in more Ju88s.