Hobgoblins and Khans - worth using?
Using them as small flanking units makes sense in small games (up to 2,5k) with not regular opponents. Not much damage output. Equipment depends on who you’ll play against, but in my opinion their role should be same as horde of Clanrats - tarpit.
If given bows you’ll get short range shooters dealing damage on same basis as night goblins. Mediocre the most. If with 2 hand weapons - good amount of low S attacks against low or none armoured units. In hobbo case I believe however in shield and hand weapon, so slowing/supportive horde or 5 models wide column. Why? I’ve been tarpitted too many times by block of 50+ clanrats with spears and shields, so I made some conclusions 
How would they do on battlefield? In my last game block of 28 hobgoblins (hand + shield) + 2 khans, managed to stop 4 Stormfiends coming from the underground. I lost like dozen of them in first round of CC, but somehow managed to kill 1&1/2 Stormfiend. Of course my greenskins had been eradicated eventually, but bought me some time for fireglaivers and great weapons to save my mortars.
Your Hobgoblins also have these throwing knives to be used in stand and shoot reaction or just on proximity.
- Khans on wolfs are famous among many discussions as re-directors and lone characters/war-machine hunters. I’ve read opinions of people who had real boners for khan on wolf - but that will not work against experienced generals with shooty armies, or when you play on 60 inches or more wide battlefield. Besides - what sort of idiot leaves cannons unguarded?
I played lot as Dwarfs and get my opponents eventually used to a surprising appearance of miners on their backs. So much, they eventually started doing the same. I also played against Skaven and had Stormfiends on my ass few times, and for the first time it wasn’t pleasant feeling (I played Dark Elves that time and eventually nerfed them with shooting and magic). Similar as with Snitch, who single handedly destroyed my 3 war-machines once. One of my opponents recently purchased Wulfrik, and I can bet money I’ll have an ambushing Marauders on my ass next time. So no. Don’t bother about Khan on Wolf.
Instead get yourself few khans on foot and add them in a hobgoblin heavy brick. Once we had 4 armies battle. long time ago one of the opponents struggled to meet the point criteria with his O&G army. I suggested him, to turn some of his Nightgoblins in the unit to a heroes. Guy set up a 50 models strong unit of Nightgoblins with 10 heroes, and they all had Great Weapons. It was all legit and … we all regretted it. This unit shattered 6 Skullcrushers of Khorne to pieces and at some point.
You can’t give your khans GW which is pity, but with S4, give them extra hand weapons, magic weapons and other items that’d fill up your 25 pts allowance. Seeing your LoA heavy army, and shitloads of artillery, K’daai & Bullcentaurs, there is a strong chance your opponent will ignore this core requirements filler of hobos. At least till 1st round of close engagement.
Don’t bother about animosity. In fact, welcome it! Where O&G animosity may cause troubles, yours has 16.6% chance to impact you in good way and only 16.6% of giving you bad results which you can easily avoid. Keep them more than 6" away from any Chaos Dwarf and Bull Centaur units to trigger animosity but within 12" from your General and BSB. On a D6 roll of 1 you have to take a panic test on LD9 or LD10 with re-rolls, should be no problem. 2-5 has no effect but on a 6 you get +1 on to hits rolls (shooting and CC) for the turn and only take D3 wounds for it, a no-brainer.
Never get the Banner of Slavery for your BSB, (a) you don’t need it with LD9/10 and re-rolls, (b) your Castellan cannot take any other magic items and (c) Hobgoblins cannot choose flee as charge reaction if they are immune to psychology, completely negating the reason you’re taking them in the first place.
So in summary - block or few of 50 or 50+ hobos with few khans inside units.
Everyone keep diminishing Greenskins role in LoA army, so prove them wrong