Minimum Validator self-Stake + Other Safety Adjustments

This proposal is intended to re-think the staking limits that are currently set on Kusama, and alter them such that, whilst keeping some degree of chaos in the backpocket, the chain remains safe over the long term. First, let’s look at the current staking limits of Kusama.

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Note that the minimum nominator bond is in PLANKs, meaning that it is actually 0.1KSM.

Recall that the NPoS election process, in order to be both successful and safe, contains 4 main steps.

Snapshot creation.
Signed submissions from staking-miner.
Unsigned submissions from validators, as backup.
Solution verification.

Our experimentation has unraveled that, as it stands now, the bottleneck for the Kusama network (and Polkadot and Westend) is the third step, and the largest input data for which this step could be executed, in WASM, without running out of resources (weight, memory, block-length), is when there are at most around 12500 nominators in the system. Note that this number is expectedly lower than Polkadot’s 22500, because Kusama opted to allow for up to 24 nominations per nominator. Thus, we need to assume the worst case in our experimentation, namely that each nominator is indeed using all of their 24 nominations.

To reflect this, we need to alter a runtime type parameter, which can only be done as a part of runtime upgrade, not as a standalone council motion. This is done in the following pull request:

https://github.com/paritytech/polkadot/pull/5000

Lastly, since Kusama network is already fully using the bags-list pallet, it can freely open its door to many more nomination intentions, being sure that the top 12,500 are selected by the bags-list. To reflect this, we suggest removing the maximum nominator count limit entirely, and keeping the 0.1KSM as the minimum bond for nominators.

NOTE: We might be able to tweak these number to slightly higher values again, once these two pull requests are merged into production:

Similar to the corresponding proposal for Polkadot with exactly the same argumentation, we also strongly advise the Kusama network to use a reasonable value for minimum validator bond. For that, we suggest an initial value of 1 KSM as a relatively low starting point, which similarly can be further increased if the need arises.

All in all, we propose the following call to be enacted on Kusama after PR#5000 is merged and enacted.

NOTE: minCommission might be altered in Ref #176 to 3% and if executed, should be reflected as well.