Most of the very best tube linestages, like the Audio Note (uk), Kondo and Shindo units have hardly any convenience or other flexible features (e.g., no remote control of volume). Some don't even offer balance control, or if balance can be adjusted, it is by way of the volume control being two separate pots (really inconvenient).
I have a custom-made linestage that I had to persuade the designer/builder to include remote control of volume and to include balance control. It took him a long time to find the parts that met his requirements.
With most high-end linestages, the priority is on quality parts and build quality and not convenience features. Such features may be included, but, only if they don't compromise sound quality. I liked the incredible features and flexibility of my Levinson No. 32 preamp, but, it does not come close to the sound quality of the two tube-based linestages I got from custom builders.
