I don't know where on the friendly-comeptitive scale you want your list to be, but i'll give my 2 cents (as a bretonnian player as well).
Your infantry is probably going to be minced by his knights. The big unit of spears might be fine (more on this later) but the small one are goners. He has 4 lances, one of which is pegasus knights which are very strong. The traditional counter to bretonnia is gunpowders, specifically str 4 ashots so the he does not get the better ward save. Most of his stuff is T 4 so you 'll be fine with crossbowmen (the longer range is very nice) and outriders. Outriders in aprticular can do minced meat of his knights, a unit of 5 can easily remove (or reduce to just one or two models) one of his horse lances. The also have fire and flee if you are afraid of being charged (with swiftstride!). The hellstorm is very bad (regardless of the opponent). Use an hellbalster although i always use an engineer with it since you are rolling 3 artilery dice. Mishaps will happen almost every turn.
The wizard on pegasus is extremely, exceedingly good. In my opinion the best lore vs bretonnians is either battle magic or demonology. In aprticualr demonology has the signature lore spell that is an amazing magic missile that hits like a unit of arquebusiers (well, better than them since you don't have to hit). He will do a lot of heavy lifting, possibly being your star player (unless you roll very badly). He also has just a lvl 2 damsel so you have the upper hand in both castng and dispelling. He is absically negating his own spells and burdening himself with the pts for the damesl. The issue with your list is that you do not have cavalry, so he has no units he can hid nearby and he will be targeted!
Speaking of cavalry, the reality is that you need it. You get counter charghe with it vs his, the basic knights are on par with the knights of the realm (roughly). You are going to need them also so that the wizard on pegasus can just hang 3" from them and not be killed.
If you really want to keep you infantry blocks, what i'd do is leave the halberdiers home and use crossbowmen or handgunners (i prefer the crossbowmen, bu either will do), also as detachements if you want but in that case consider smaller units of 5 also so that they can support the spearmen.
They will need all of the help in the world, but if you play you dice right (or put the familiar that lets you pick spells on the wizard) you should be able to cast the hex from demonology on the enemy for -2ld and -2 I, and the N.6 enhancement on your spearmen for +1 to T, M and I, which combined with your +1 ti I from the spear might make your spearmena ctually strike before his charging knights (you 3+1+1=5, him 3+3-2=4)!
Another choice is elementalism with the earthen ramparts spell, which gives a 5+ ward and a low linear obstacle (i.e no I binus when charged) but the daemonology has an overall better use thanks to the signature spell.
If you manage to fork the pts, i'd also either put the general on griffon (the smaller one is fine) or use a bsb captain on griffon (they are both around 250pts with ward saves). they are both amazing, cheap, small monsters that compensate two very lacking combat characters (i mean, he is play a duke that is gonna simply kill him the first chance he has) and are extremely deadly to cavalry, sinche if maneuvered right they will charge on the flank and blunt the lance.
I thought of something like this:
===
empire 1250 [1250 pts]
Warhammer: The Old World, Empire of Man
===
++ Characters [520 pts] ++
Captain of the Empire [242 pts]
- Hand weapon
- Lance (if appropriately mounted)
- Full plate armour
- Shield
- Battle Standard Bearer
- Griffon
- The White Cloak
Wizard Lord [225 pts]
- Hand weapon
- Pegasus
- Armour of Tarnus
- Lore Familiar
- Daemonology
Empire Engineer [53 pts]
- Hand weapon
- Repeater handgun
- No armour
++ Core Units [384 pts] ++
24 State Troops [159 pts]
- Hand weapons
- Thrusting spears
- Light armour
- Sergeant (champion)
- Standard bearer
- Musician
10 State Missile Troops [75 pts]
- Hand weapons
- Crossbows
- No armour
- Sergeant (champion) [Crossbow/Handgun]
6 Empire Knights [150 pts]
- Hand weapons
- Lances
- Shields
- Heavy armour
- Preceptor (champion)
- Standard bearer
- Musician
++ Special Units [226 pts] ++
5 Outriders [101 pts]
- Hand weapons
- Pistols
- Repeater handguns
- Heavy armour
- Sharpshooter (champion) [Repeater handgun]
Great Cannon [125 pts]
- Great cannon
- Hand weapons
++ Rare Units [120 pts] ++
Helblaster Volley Gun [120 pts]
---
Created with "Old World Builder"
[https://old-world-builder.com]
