It seems like I've been sketching this one for ever. It's smaller than the Mk3 (only 1.5m at its longest) and suffers from not enough ammunition - but it can fly. Perfect for zero-g combat and ideal for GMs who love to catch the players off guard by having the Droid appear in the very last place you would expect it; even by sneaking through the Mesh ducting.
It's a Droid that fills a gap for me, I want it to sneak up on my players and cause havoc. I want it in small spaces. I want the Droids to be less predictable and the Mk5 gives me that. The downside, it's not very large for ammo!
I like the flaw. I also like the idea of "More of them!". I need to have flaws in the Droids because they were never really finished in design or tested by humans. I like the solution of having more - you can always have more! I also like the idea of a machine that can improvise but has never had to work out how to fight without guns!