Well, yes it is theoretically possibly but most mechs I have seen don't really have blind spots. The winner of the Spartan vs Landmate battle would be whoever had the most skill, which considering how horrifying spartans are would probably be them, they used to beat up their trainers who wore landmate grade armor (after the spartans accidentally killed 3 trainers in practice bouts) and this was before the spartans had their suits, they were wandering around in a cave wearing skin tight black bodysuits, which when they asked the lead trainer he could only respond "I have no idea where they got those suits." however Spartan IIs are freaking rare and the only ones truly worth mentioning, since the Spartan IIIs mostly got themselves dead they weren't as well trained or equipped, they got those lousy scout armors which don't really provide much protection aside from stealth, which only worked at long distance so really it was fuckin useless all things considered, I blame Ackerson for that, thankfully he got his in the comic book.
Creating Spartan IIs is totally possible, most of those procedures would probably work given time and effort (and potentially a real life Dr. Catherine Halsey) The big point of using landmates would be to give the spartans extra mobility and combat capability (tougher, bigger guns, roughly same speed) but a spartan wouldn't fit in a normal landmate it would have to be bigger not much bigger but still bigger, since the Master Chief himself is 6'10" outside his suit, and he is physically average amongst spartans, it is his wonderful brain that makes him so awesome.