Wow! I was just working on something very similar, (go+riotjs) after frustration with LaunchDarkly. Encourage you to offer paid SaaS
May I ask what specifically you found frustration with LaunchDarkly?
I paid for some tier, didn't like off-prem, v1 didn't have vairant (was bool only), upgrade to v2 was bumpy, their php-client did some odd stuff (background shell_exec) the support didn't even know about.
CEO was nice enough, refunded some of my money.