We tried the "make one howitzer do everything" silliness with 155s and that's just stupid. The beasts are large, bulky, heavy, and hard to find enough geography to deploy and the ammo piece is 90% of the logistic load for a division. Our bean-counters have tried for years to show that making one gun do all save us money and fights all enemies in all situations handily but that has always been poppycock.
We still need and 105/120 medium-caliber expeditionary high rate of fire direct support howitzer for mobility and responsiveness and we will still need mass and reach and flexibility in our GS weapons.
I see no compelling advantages for SP artillery.
Put me in the “Towed Artillery is lighter, cheaper, faster, and more durable” column.