How to modify network params and restart the chain w/o Genesis regeneration?

[eugene-eko2000]

Hi, I'm thinking about making modifications in our testnet configuration.
I'm considering the following:

• changing nodes number;
• changing network params, e.g. seconds_per_slot;
• running more modes on different machines and configuring them for being a part of existing chain;

Could you please chare some examples if they exist?

Thank you a lot in advance!