Bren doesnt magically appear as a Wasp on its first encounter with the enemy; it can easily be killed on that first encounter, or Ostheer can capture a decent portion of the map and set mines or something when it has the advantage.
The Wasp seriously has a very limited window, and IMO Brit is better off teching really fast for RE's, sniper, etc instead of wasting 15 fuel on UC which slows teching really bad. When Wasp dies, 222 rolls around free while you dont have any counters right away.
if the bren dies, you played wrong (or, on the other hand, you could just say that the 222 can also easily be killed by small arms). it has superior range and speed, and comes at a time when no mines could possibly be anywhere. even by the time you can get the wasp, which is at roughly 5 minutes, the area where any mine could be is very limited. theoretically you could just send the wasp into his base and prevent him from ever building t2. it is getting nerfed for a reason after all.