Built-in MIDI sequencer in an instrument VST ist asking for a lot for a small price. When you want it cheap, you can get by putting the time in tinkering. E.g. looking in archives for a free ancient fiddle .sf2 package, a soundfont player and a sequencer you can save together as a FX chain (though not in that order ;) ) When you want it convenient, you can trade off that time against paying for Kontakt, Falcon or whatever fiddles your fancy.