several factors could be added in to balance them out.
1: Crossbows benfit less fro mskill progression then bows IE bow's get bigger boost to damage via skill. crossbows stay more constent. Perhaps only gaining boost on the classic "25 point" gamesas thresholds.
2: While packing much more punch then bows of "equal" material rating are noticeable slower (bow's shoot like 2-3 arrows) for every one from a crossbow.
this way crossbows would kill enemies that could take say 1 arrow with only a little health left in one shot instead of having to load up, aim and fire off another arrow. So in the long run bow's would be "more upgradeable" then Crossbows with skill but suffer from weaker damage per bolt. Crossbow's disadvantage is skill effect them less, and they reload slowly and perhaps even suffer from reload interruption in melee as well as slow speed while reloading.
The first would be a very realistic and balance-friendly tweak.
If Crossbows, for example, had a
fixed damage amount of 40-50 damage (60-70 for the dwemer version), then anyone not perking archery now has a reason to use it. For those that
do perk archery, then bows come out on top at some point. This would reflect the idea that bows are objectively superior, but require far more training to master.
Some other realistic tweaks they could do might involve bows simply having more accuracy at longer ranges (if they don't already?) and simply making the reload speed gap a bit more noticeable.