Is this added versatility to the Sorcerer's Flexible Casting imbalancing?

Question

After playing Sorcerer quite a bit (both spell-slot and spell-point versions) I feel that the spell-slot variety lacks much of the versatility granted under the spell-point option.

The current Flexible Casting feature allows you to turn a spell slot into a number of sorcery points equal to its level and you can convert a number of sorcery points into a spell slot following this table:

$$ \begin{array}{|c|c|} \hline \text{SPELL SLOT LEVEL} & \text{SORCERY POINT COST} \\ \hline \text{1st} & \text{2} \\ \hline \text{2nd} & \text{3} \\ \hline \text{3rd} & \text{5} \\ \hline \text{4th} & \text{6} \\ \hline \text{5th} & \text{7} \\ \hline \end{array} $$

However, I found this particularly lacking when it comes to spells that don't significantly change when upcast (such as misty step). Thus I wanted there to be a way to turn these larger spell slots into smaller ones and propose the following addition to Flexible Casting:

As a bonus action, you may convert a spell slot of 5th level or lower into any combination of spell slots so long as the sum of their levels is less than the original slot. For example, a 4th level slot could become a 3rd level slot, a 2nd level slot and a 1st level slot, or three 1st level slots.

Nothing changes when converting slots into sorcery points.
Converting a slot into sorcery points is always worth more than converting the slots you make out of it because of the sum having to be lower than the original slot's level. (If you make a 4th level slot and convert it into different spell slots, you couldn't earn back more than 3 sorcery points)

Nothing changes when converting sorcery points into spell slots (one exception).
The cost of creating the composite slots is less than or equal to the cost of creating the larger slot. (Making three 1st level slots costs 6 points, and making a 4th level slot, which can be turned into three 1st level slots, also costs 6 points).

The only exception to this is that a 5th level slot can be turned into four 1st level slots, which would ordinarily cost 8 sorcery points, but now would only cost 7. I'm not particularly worried about this one instance of a price mis-match though.

Things change when comparing the costs of making slots from other slots (the whole point).
Ordinarily, if you start with a 5th level slot you could turn it into 5 sorcery points, and turn those into a 1st and 2nd level slot. This rule lets you turn it into a 3rd and 1st level slot which would usually require seven sorcery points, not just five. This is entirely intended and is because you can now convert slots into new possible sets of slots.

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Something like converting a 5th level slot into four 1st level slots to cast catapult four times is what I'm worried about though. Cast at 5th level, catapult would deal 7d8 damage, but now it can be split into four instances of 3d8 damage (a total of 12d8). This deals 5d8 more damage than the previous version, though it requires 3 more actions, and a bonus action. Alternatively you could create two 2nd level slots dealing only 8d8 damage, costing an additional action and a bonus action. I'm unsure how balanced these damage differences in particular are though, especially given that there are many, many spells.

Is some part of this proposed change to Flexible Casting going to imbalance my games?

Answer 1

Per your last bolded section, yes, you do create more damage by allowing more castings of lower level spells instead of a single higher level casting, but you also wreck your personal action economy. To get that 12d8 damage you're spending four times as many turns doing the damage. In most normal combat situations, that is generally a poor trade. It does give you some more endurance to keep putting out damage all day, but, well, you had a fifth level slot to spend in the first place, so you aren't low level. Is that 3d8 damage from your catapult spell doing much more than you could already do with cantrips?

So in terms of the damage trade-off, this doesn't feel unbalanced at all. If it were a wizard or other caster with lots of non-damage effects, I'm sure with time and spell knowledge someone could find a way to break it, but with the sorcerer's limited spell list, that seems less likely.

Probably not, because the loss of action economy is typically worth less than the raw total damage. Remember that a fighter can make 14,400 attacks in a day (exhaustion not withstanding), and you can do the same with your cantrips, so you converting a 7d8 catapult into a total of 12d8 over several turns still doesn't compare. The 7d8 is still better for downing the enemy the fastest; if you've got all day, spend all day. For that matter, witch bolt does 10d12 when cast at first level... Things like charm person or earth tremor are probably the only things you need to watch for - area knockdown or effective control are a lot scarier than nearly doubled damage by spending four times as many turns.

(My only seriously run 5e character so far is my Cleric; my first thought was that I'd love to split my second level slots that are mostly concentration buffs into multiple first level guiding bolts, giving our rogue free sneak attacks... )