It’s only fair the logs (or Ewoks) also get the Warhammer treatment.

Some potential options:

• strap some propulsion on the ends of the logs
  • upgrade to warp drives to use them against space vessels
• the logs are tougher than any metal and heavier to boot
• warp fuckery means the logs ignore armour or directly affect the people inside in some way (feel free to add chaos god shenanigans)
• Ewoks believe the logs will work and they have the numbers to affect reality
• the logs just hold the walker for the split second it takes to get swarmed by Ewoks or otherwise dealt with
• the logs explode
• Ewoks are all force users now

Though let’s be honest: even with all that, the Ewoks probably would’ve been one of the countless species wiped out during the Great Crusade. 40k does have some argument for having only the most over the top shit existing.