I haven’t had any problems with thralls refusing to use the “wrong” type of weapon recently either. A follower who came out of the, um, training center, with a one-handed weapon will happily use a spear or two-handed sword, and someone who was a spear-user before enlightenment will use a truncheon or war axe with no protests.
The only problem I’ve seen is that if a thrall has a two-handed weapon and a shield in their inventory, they may equip the shield, and then get confused because they don’t have enough hands for the weapon anymore, so rather than packing the shield and equipping the weapon they try to attack without weapons.
I take Exile thralls on training trips to the Giant Spider when they’re level 4 or something. Never lost one to poison yet. The Spider Queen’s attacks are so slow that the thrall never accumulates a high stack of poison. I find Bleed more dangerous to low-hitpoint thralls, so don’t let dagger-armed NPCs gang up on your thrall (or yourself, for that matter - bleeding can be harmful to your health).