Can a non-WC19-compliant wheelchair be retrofitted to include the 4 securement points?

While this is certainly possible and is allowed by WC19, manufacturers currently do not offer the option to retrofit attachment of four suitably strong securement points. For most wheelchairs, some design modifications would be necessary to achieve the required dynamic strength, just adding a retrofit kit of four bolt-on securement points would not make the wheelchair strong enough to comply with WC19.