This is my proposed tier system for torque asset types to simply the addition of more assets and to reduce the confusion about the margin maintenance level for various pairs.
Base margin maintenance: 105%
Margin maintenance adjustment (MMA): the amount over the base margin maintenance that will be added to the loan for both the collateral and borrow asset types
Tier 0
MMA 0%
Stablecoins
Tier 1
MMA 10%
ETH
Tier 2
MMA 15%
WBTC
Tier 3
MMA 20%
LINK, YFI, AAVE, COMP
Tier 4
MMA 25%
MKR, KNC, BZRX, LRC
To find the margin maintenance level for a given loan, just add the MMA values for the collateral and borrow asset types to the base margin maintenance amount.
Example 1: Borrow WBTC (Tier 2) using ETH (Tier 1) collateral
Margin maintenance level is 105% + 15% + 10% = 130%
Example 2: Borrow AAVE (Tier 3) using YFI (Tier 3) collateral
Margin maintenance level is 105% + 20% + 20% = 145%
Example 3: Borrow USDT (Tier 0) using LRC (Tier 4) collateral
Margin maintenance level is 105% + 0% + 25% = 130%
This method could be used for determining the liquidation markdown for each pair too.