You can ease into gouache gradually. Get a tube of white gouache (I like the Da Vinci brand). You can mix it with your watercolors to make lighter shades, and you can use it for white instead of leaving the white of the paper (which looks a little unnatural when you are painting opaquely). You can phase in other gouache colors as your watercolors get used up.

Beware of using thick layers of watercolor or gouache. It gets brittle and can crack.

I learned quite a lesson many years ago. I was in a water color class where we were all painting different subjects. One of my class mates, an older woman, was having trouble painting flowers. She had a thick painting style. A fellow classmate (not me) was gently cajoling her about her thickly painted flowers.

That is when the teacher broke in their conversation and said to the cajoling student “…You better watch it. If she gets a handle on her flowers she will be selling all her paintings and yours will be gathering dust…” We later learned our instructor, a landscape painter, spend most of the summer months making flower painting to sell. He later told us he was selling out all his flower paintings he did every year in the summer and that demand for them had out stripped his ability to make them.

Here is an example of what sells:

http://www.jeanhaines.com/gallery?g=11

I think you should do what you love but if you love thicker paint maybe your journey is taking you to another medium such as acrylic or gouache. The skies the limit. But since you have watercolors experiment try a poinsettia with more water, get into the feel of the medium its quite enjoyable. I’ve seen some beautiful florals done with watercolor that were either more opaque or more transparent. Your painting is beautiful.

Artists can push the boundaries of the rules, but there is already a medium that wants to be painted in thick layers.
I came to watercolors from acrylic painting. A tube of Winsor & Newton Professional acrylic paint in ultramarine blue sells for $7.79 for a 60 ml tube. Same color and brand in watercolor is $6.48 for a 5 ml tube. These are current sale prices, the WC tube is usually about $9.
Thats $0.13 per ml for acrylic and $1.29 per ml. for watercolor. Other brands, colors, sizes, and sales are different prices, but the outcome is the same. The same painting will cost significantly more when using watercolors in thick layers than if done in acrylic.
My watercolor paints crack in the palette when left to dry in thick layers. The cracking is likey worse on flexible paper. The paper sizing is not being wet enough to bond the thick layer of watercolor to the paper. Seems likely that thick watercolors could crumble and fall off the paper.
The plastic binder in acrylic holds the paint to the paper and keeps it from cracking.
In acrylic paints, you can apply the paint in thick layers without the disadvantages.

I don’t want to talk you out of watercolours, but you can keep acrylics wet by misting with a spay bottle or by using a Sta-Wet palette that has a big spongy thing underneath a disposable palette sheet.

Noelle