First question: How many battlewagons do you have?
Second question: What's in each of them?
Third question: Do you have a big mek with a
KFF in your list?
General answer to your question: No. Don't do it.
Between the grot riggers on each of your battlewagons, the
KFF's mek's tools, the ability to take a grot oiler for a reroll, you have the ability to repair any given battlewagon with three attempts in a given turn.
The rest of the explanation depends on the answer to those three questions though. My 'Ard Boyz list had 4 battlewagons; 20 boyz in one, 20 boyz in a second
KFF + Nobs in a third, Ghazghkull with burnas in the 4th. 90% of fire incoming at the battlewagons was directed at the
KFF wagon (in the middle) who incidentally exposes no side armor.
If you're running battlewagons at 2500 without a
KFF, with less than three, you're probably doing something wrong.