Prop 444: Composability Incentives Category

This proposal would add Osmosis Liquidity Incentives to pools essential for bridging composability on Osmosis.

## Category Details
The composability category is intended to provide small, fixed incentives to stableswap pools between identical assets with differing sources in order to facilitate trading on Osmosis through the deeper canonical asset pools, regardless of the origin of these assets.

As a category that operates in the background, pools added to this category will not be expected to be added to the main Osmosis.zone frontend.

## Initial Pools
Initial pools included in this category would be:
* USDC.axl/USDC.grv
* USDT.axl/USDC.grv
* USDC.axl/polygon.USDC.axl/avalanche.USDC.axl

## Establishing Targets
Based on typical trading volumes in the current USDC.grv/OSMO and USDT.grv/OSMO pools require approximately $95k and $130k of liquidity respectively to facilitate trading to and from Gravity Bridge. As the intended composability pools are StableSwaps they are far more efficient than Balancer pools at providing the same function and so require approximately 3x less liquidity to facilitate trades at the same slippage.

Conversely, with the lower levels of swap fees in these pools a much lower slippage should also be targeted. Converting the 0.2% swap fees to 0.04% results in a proportional target of 0.2% slippage.

We can therefore target specific liquidity for slippage levels. This is calculated in this spreadsheet and results in $45k of liquidity in a pair being required to cater for OSMO/USDC.grv trades and $62k to cater for OSMO/USDT.grv trades if they were StableSwap pools. This may be excessive as the APR from external Gravity incentives provided in Proposal 347 makes these pools attractive and there will be activity from people wanting to join for the rewards rather than using them as a way to utilise Gravity Bridge. A baseline of $45k liquidity from incentives alone will therefore be established.

Now the target Liquidity is established we need to identify an attractive APR for this liquidity level. Comparing alternative stable/stable pools across the Interchain shows that typical yields range from 12% to 28% APR. As additional fees will be generated from swap fees, 12% will be set as a reasonable baseline reward rate.

## Rent vs Buy
As the total OSMO spend on incentives is relatively small at the intended liquidity targets, acquiring this liquidity through incentives in the more cost-effective option for approximately 5.5 years before purchasing the liquidity outright became a preferable option. As cross-chain bridging routes are still being established and may be subject to change with the release of native USDC on the Interchain, renting through incentivisation is also the more flexible option.

## Requested Incentives
Bringing these together, to establish $45k liquidity earning 12% APR OSMO rewards requires a target of ~15 OSMO a day, which is a minimum incentive setting of 0.0062% per pool, resulting in around 0.02% of actual emissions going to each pool.

The USDC 3pool requires 1.5 the liquidity and spend of a pair and so needs an emission setting of 0.0093%, resulting in around 0.03% of actual emissions going to this pool.

This proposal asks that this be set as a fixed level of incentives for every pool added to the composability category to provide functional liquidity for bridge composability. These incentive levels would be set after this proposal and remain in place unless revised by a future governance proposal.

Commonwealth Thread: https://commonwealth.im/osmosis/discussion/10057-composability-incentives-category