Well, how much of a particular profession can you really learn in one year? Given the skill points you're given per lifepath, dividing the time increments would lead to some awkward fractions in the math. You could work around it, but I honestly can't say it's ever struck me as a vast drawback of the system. *shrugs*
As I understand it, a direct piercing sword-thrust with a strong run-up could penetrate mail or plate, at least if you aim for the weaker points at the joints. It depends whether you're talking about damage-as-accuracy or not, and whether it's a slashing maneuvre or piercing damage, etc....your system might end up with people being cut by swords while wearing mail or plate. (A sin even the great TRoS has!)
You might, just conceivably be able to improve on BW/TroS in terms of combat simulation, but given the benefit of consultation with actual medieval swordsmanship experts and years of playtesting, the odds of an informal community-led effort doing much better are slim. Exediron has made some excellent points about the relative merits of weight, fatigue, weapon reach, etc. (reach being very important, since a honking great longsword is useless at close quarters,) but about 90% of these dynamics are already covered extensively in Burning Wheel. Stick a fork in it- it's done.
Frankly, I think all the emphasis on combat realism in this thread is a little misplaced. I'd like my game, at least, to incorporate some of the more... liberating aspects of realism- such as NPCs that actually behave like independent agents, rather than puppets of GM railroading, and PC decisions+dice-rolls that actually have consequences, even when it conflicts with "the plot". What mechanics are we going to use to ensure that, exactly?
More generally, what is our stance on IC vs. OOC information? This is a subject of huge concern to many groups with simulationist inclinations, but it's treatment within the hobby is also riddled with double-standards and superficialities. (I'll put this bluntly: GM dice-fudging IS metagaming, because physics doesn't know about your plot.)
How do we intend to handle social conflicts within this world? Some players feel that systems like the Duel of Wits are obtrusive and artificial, but the problem with leaving the solution of inter-PC disputes purely to the real players talking it out is that it becomes harder to factor out real-world emotional baggage. In other words, it often leads to less in-character behaviour, not more.
Compared to these problems, the question of, say, how to square the inclusion of magic is a relatively minor concern. All of the above are rather more likely to be significant bones of contention, and I haven't mentioned anything about the problems of geographic scale and time-keeping, economic cycles, personal investments and crafting skills, etc. etc. etc.
Those would all most likely demands threads unto themselves.