You mean your single stream of HTTPS traffic to a known destination 24x7?
What if you only use the HTTPS VPN when necessary, e.g. for streaming Netflix (seeing that they've been a target before), but for regular browsing, email, DNS, etc. you don't?
Lack of DNS queries for one small example.
There are enough differences between HTTPS and VPN protocols to be able to distinguish them using DPI. IDS/IPS vendors even show this as a feature usually.
There's protocols like stunnel that hide your arbitrary TCP traffic in a TLS tunnel that looks like web traffic.