You actually don't want the tank hotter than it takes to allow the wvo to flow easily. In Houston that almost happens year round at ambient air temp. 
What you want to concentrate on is getting the engine warmed up as fast as possible and getting the wvo as hot as practical prior to the injectors.
This is pretty easy.
Use a FPHE to warm the wvo to near engine coolant temp prior to the IP and high efficiency injector line heaters to get it as hot as possible prior to the injectors. 
The main difficulty in short trips is completely purging the wvo fuel from the IP and injector lines prior to engine shutdown and resisting the temptation to switch to vo before the engine has reached full operating temp. You can put an inline thermo switch in the "VO on" circuit to avoid the second and add a delay circuit in the "ignition off" circuit.  This won't guarrantee that VO is used optimally (for engine life) but it helps.