Boros Humans White

[DerWille]

Since rotation has hit, I want to port over my Boros Humans White deck from last season into modern and make some upgrades to it. I'm also a complete newbie at modern. All last season I just played my standard deck and got some halfway decent results. I'm looking to build something that will give me a good shot at winning some modern events around here without breaking my wallet so I can grind more cards up.

Boros Humans (Draft 1)
[deck]
Creatures (30)
Champion of the Parish x4
Elite Vanguard x4
Boros Elite x2
Thalia, Guardian of Thraben x4
Accorder Paladin x4
Lightning Mauler x4
Silverblade Paladin x4
Hero of Bladehold x4

nSpells (8)
Lightning Bolt x4
Brave the Elements x4

Land (22)
Sacred Foundry x4
Clifftop Retreat x4
Plains x9
Mountain x4
[card]Slayers' Stronghold[/card] x3
[/deck]

This was my first pass over this, but there's a few cards that seem good, but I don't know where to put them or if they should be included at all.
Soldier of the Pantheon: He's probably a strict upgrade over Elite Vanguard. Once I get 4, I was thinking +4 Soldier of the Pantheon, -2 Elite Vanguard, -2 Boros Elite
Honor of the Pure: So +1/+1 to everything that isn't named Lightning Mauler. That's awesome.
[
card]Path to Exile[/card]: Remove any annoying creature for 1 mana? Sounds good.
Lightning Helix: 3 damage and heal 3? I like that too.
Mirran Crusader: Pro-black and green with double strike seems relevant, but Silverblade Paladin seems stronger, damage wise at least.
Sublime Archangel: I can try porting over the Wescoe's former World's deck combo instead of running Hero of Bladehold
Elspeth, Knight-Errant: She could be the 4 drop instead of Hero of Bladehold. She can survive wipes and other shenanigans and generate some VCA.

Mana base
The only upgrade I can think of is running 4 Arid Mesa in there as well, but I don't have sort of money (yet). Are there any other [mana]R[/mana][mana:
20ucs2td]W[/mana] lands I should be aware of? Should I run different spell lands? Stronghold's +2/+0, haste, and vigilance was super relevant last season, but I wonder if it's too slow for Modern.