WordPress Subscription Promo Manager

I run a WordPress site that sells recurring memberships and I need a developer who can turn my manual subscription rules into a streamlined, code-free workflow.

Current plans
• Scenario 1 – $1 first month + $25 admin fee, then $50 every other month
• Scenario 2 – Pay the yearly rate and get the last month free

What I need built
1. A simple dashboard inside WordPress (a small custom plugin or a clean WooCommerce Subscriptions extension is fine) where I can:
• Toggle promotions on or off: First-month discount, Admin-fee waiver, Extra free entries after a set period, and “Pay the yearly rate and get the last month free.”
• Add, edit, or retire future promotions without touching code.
2. Logic that prevents plan switching once a customer enrolls—users must stay locked to the offer they joined on.
3. Automated invoicing that clearly lists: chosen plan, any discounts applied, and the schedule of upcoming charges. PDF or email—either is acceptable as long as it looks professional.
4. Clean, well-commented code so I can hand it to another admin if needed.

Nice-to-have
If you can surface quick metrics (active promos, number of locked-in users, next billing totals) in the same dashboard, that would be a bonus.

Please outline:
• Your approach (plugin choice or custom code).
• Estimated timeline to deliver a working prototype plus any testing you’ll include.
• A brief reference to similar subscription projects you’ve handled.

I value clarity and maintainability over flashy extras, so keep it lean, reliable, and future-proof.
I currently have some subscriptions, so the solution should not affect existing ones.