The equivalent of the chunks hanging off the back of Headstrong and Tantrum and assorted kibbly bits on Razorclaw were literally their own robot in the Devastator team, being Long Haul - the lower abs/crotch/thighs of the combined mode. Long Haul who, as you pointed out, was a fairly compromised figure for that purpose.
Again, if they didn't just ape the G1 designs I'm almost certain they could have had a better solution than just sticking the thigh block on the back of the leg forming robots.