I would quite happily spend the kid’s inheritance on a decent Bass VST plugin - something up to the standard of the wonderful GA4!
I’ve got more synths than I can poke a stick at (KU11!) and enough virtual instrument to see this life out, but NOTHING in the virtual bass department. The old Virtual Bassist deserves to be reincarnated for the 21st centrury. I have a bucket of money ready to throw at the first company who can sell me a good MIDI bass VST that works along the lines of GA4 or Toontracks EZ Keys or EZ drums. Anyone?
You may not be looking for a third-party solution, but just in case you hadn’t yet seen these:
Vir2 BASiS is an excellent collection of electric, upright, fretless, and synth basses. It provides multiple velocity layers, legato and vibrato tools, release layers, harmonics, plus a variety of performance techniques such as slides, slaps, hammer-ons, pulloffs, rakes, and falls. One of the best virtual bass instruments I’ve seen, and it often goes on sale in November.
Ilya Efimov produces a fine selection of detailed bass libraries, currently on discount.
I understand the original post is a feature request for Steinberg to produce a bass VSTi, and both of the above solutions are Kontakt libraries; just wanted to add a couple additional possibilities.
The possibility of new versions of Virtual Guitarist and Virtual Bassist was teased not too long ago:
I found BASiS kinda underwhelming compared to the other Vir2 libraries. I’ve not tried the Ilya Efimov stuff.
Spectrasonics “Trilian” comes to mind. I’ve been using it for the past 7 years & haven’t found anything that comes close to its realism. You’ll have to create your bass lines though. Come to think of it, existing midi bass lines in various genres are just about impossible to find. And if you do decide to take a look at Trilian, keep in mind that these libraries (along with Omnisphere 2 etc.) are very demanding and an SSD or better storage solution has to be considered. Good luck!
Ooooops… I’m in the “feature Requests and Suggestions” forum. 
Carry on, there’s nothing to see here!
Those are very good. Scarbee makes some great ones which you can get from Native Instruments. And Trillian is fantastic as well. I think that should cover it.