I've stopped playing until there's an overhaul, so I don't know for sure, but I couldn't figure out how to upgrade existing units, or if it's even possible.

I loved being able to assassinate my own faction members in Medieval Total War 1. Pity it was taken out in the sequels. Would be a cool touch here.

One of the actions on the action tab is disband unit.

Yeah, nothing like getting a few level ups in a unit only for them to be completly outdated afterwards when you discover higher squads or better gear. I noticed there was an "upgrade" option when designing a new unit. At first I thought, hey I can click this and give them leather armor instead of the patchy rags they're wearing now. But no it just designs a different unit that you can train. Which is kind of pointless since if you're designing a new unit you won't be keeping much of the old stuff on it.

You really think whole companies of mercenaries were put out to pasture because they couldn't figure out how to adapt from a short sword to a longsword effectively?  Of course not.  You may get put out to pasture because everyone's coding in Python now and you never learned anything but COBOL, but medieval warfare was not so highly sophisticated that it took years to master the technology, at least so far as swinging bits of pointy metal at the enemy.  Prior to the industrial revolution about the only time that ever happened was near the end when advances in musketry started to really obsolete the old cavalry and pikemen mix.

Part of the problem, of course, is that historically weapons technology advanced by ages, not by months.  No medieval armorer went scurrying happily up to his king to announce that they'd figured out a way to make their swords a foot longer, whereupon the king ordered the training of an entirely new army to use these advanced new weapons.  Elemental's technology advancement is deeply weird when it comes to such things, going off of the idea that you're uncovering and relearning old technology rather than inventing something new, and thus can go from figuring out how to make sharp sticks to forging magical longswords in less time than it takes a child to grow to adolescence.

Regardless of the time scale, though, producing a medieval-tech soldier requires several things: crafting weapons and armor, recruiting men, training them to follow orders and not run away from giant spiders or other soldiers, and training them to use their weapons and armor.  All these aspects are not so holistically linked that it should be impossible to save a bit of time by resupplying and retraining a soldier with new weapons.  New armor should be even easier.  That said, the base training time should be a lot less static than it is now.  Longbowmen should take significantly longer to train than other units, for example.

Just send them to their deaths in a stack - you get some benefit of minor damage/wasting enemy turns and you get rid of the unit.

I agree with Cree (hey, I'm a poet and I didn't even know it!) - it would certainly be Most Useful if we could upgrade our old troops. You know, the ones with all their experience, which we've had running with us for years?

I, too, would really like to see units merging into squads.  With regard to disbanding units -- yeah, you get citizens back, but you've lost all those precious gildar, which so far I never have enough of.  With regard to upgrading -- it'd have to have a cost: perhaps the difference in gold and metal from the original to the new?  And perhaps costing some training time?

Forward scouts!  Spread our your older obsolete units across your frontier and use them to push your view as far into enemy and friendly territory as you can!  A few properly placed scouts can save you the mana of having to teleporting your hero at the last second, and most importantly, it lets you see the composition of the stack heading towards your cities.  Also I never want my champions without a clear something to do, so if I'm sending them out to kill 3 spiders and a rogue, for goodness sake I want those spiders and rogues so well scouted that my champoin doesn't waste a single move in his "death sweep" to take them out.

Also with scouts of obsolete uints spread around your enemy's border sometimes the AI sees one of them as a threat tends to lash out, which gets him out of position for your real stack.  In my current game I have so many obsolete single units spread out that I can see like 95% of the map.

TERRIBLE example, my man. 

Windows 7 Home version, FULL!   $180.00

Windows 7 UPGRADE version!       $109.00