I'm not sure about your assessment. Against a fairly ordinary player combat build you have 32 seconds of shielding under sustained fire (if you put all power to SYS) and not enough speed to break mass lock. With balanced pips, shields down in 17 seconds.
Bulwark vs Engineered PmkII
My trade cutter only carries 672 tons and can handle maybe 2 NPC Anacondas (one at a time) with system security to assist. Against players it has to run, and medium ships (can't outrun) will gank me every time. (To be fair, I've improved a bit and upgraded to prismatics since last time anyone tried, but a
good PVPer would have no issues against me). The 64 tons of potential cargo I give up for size 6 prismatics just so I can
maybe break mass lock and run means I frequently have to take an additional run to finish a cargo mission, and the fact that it has cargo bays at all means it isn't optimized enough to
defeat a player ship in combat. Even if I did break mass lock and run, as the OP noted, I'll just get interdicted right back to where I ran from.
Completely off topic--why do you have an interdictor on your "trade" ship?