I have been seeing some interesting arguments around the internet in regards to this topic and I would like to weigh in and have a discussion about it. Magic is supposed to come to sorcerers much easier than any other spell casting class, even wizard. It isn't a learned art for them, but a manifestation of personality and emotion.
With how easy magic comes to them, they should have the most flexibility when casting their spells. I have seen the argument that in previous editions, sorcerers might have been too flexible, however they had a very limited number of spells they knew, particularly when compared to now. Granted a lot more was tied into heightening spells in previous editions and they hard more spells slots, where as now all casters have the same base number of spell slots, making them all equal in this regard.
Sorcerer does not prepare spells, they simply know spells and they are innate for them, however when ever they learn a spell in a spell slot, it is stuck at that level unless they learn it at a higher level. In comes Spontaneous Heightening at 3rd Level.
"SPONTANEOUS HEIGHTENING
You learn to freely heighten some of your spells, even if you know only the base version of the spell. During your daily preparations (see page 192), you can pick up to two spells you know. You can cast those spells using any applicable higher-level spell slots you may have, heightening the spell to the level of spell slot used, even if you don’t ordinarily know the spell at the higher level."
Bard works the same way, however they Additional Heightening at 8th level, where as the sorcerer does not get it at all. Bard is also more of a learned spell caster where sorcerer is innate.
"ADDITIONAL HEIGHTENING
You can heighten addition spells. Spontaneous daily preparations, when selecting spells for spontaneous heightening, you can select up to four spells instead of two."
Wizard on the other hand has to prep spells before hand, but can heighten any spell in their spell book to any level spell slot they have when memorizing their spells. They also have the ability to easily surpass Bard and Sorcerer in number of spells known. Finally they get Quick Preperation at 4th level, which actually has a very high degree of flexibility, even more so than Additional Heightening in most places and the 10 minute requirement is very easy to meet.
"QUICK PREPARATION
You can spend 10 minutes to empty one of your prepared spell slots and prepare a different spell from your spellbook in its place. If you are interrupted during such a swap, the original spell remains prepared and can still be cast. You can try again to swap out the spell later, but you must start the process over again."
With these examples in mind, sorcerer really falls behind when it comes to flexibility and really loses the theme of what they are supposed to be. This is the real issue and why they should spontaneously heighten any spell they know. This perhaps would also allow the Divine Sorcerer to make up for the fact that they don't have a channel ability like a priest.
If sorcerer were able to heighten any spell they cast, a new issue then arises with the fact that they would now have so many spells know that they become too flexible. That is a simple fix, decrease the number of spells they know.
Reducing the number of spells known and being able to heighten any of those spells, would certainly streamline the sorcerer in many aspects.
