Not sure you could do that if you wanted to keep the client and simply make them inactive. A client without a contact seems problematic.
If you are looking for relations on the client_id then there are some others.
module_client_meta - Blesta Core
client_notes - Blesta Core
client_packages - Blesta Core
client_settings - Blesta Core
client_values - Blesta Core
reseller_pricing_clients - Reseller Pricing
support_tickets - Support Manager
You should also be concerned with tables related on the contact_id
accounts_cc, accounts_ach - Blesta Core
contact_numbers - Blesta Core
contact_permissions - Blesta Core
log_contacts - Blesta Core
support_replies - Support Manager
download_logs - Download Manager
mass_mailer_tasks - Mass Mailer
I think that covers everything you missed.