Has Body Pump or Pilates been added please?

You can just create it yourself. Create a new activity using cardio and rename it "Body Pump." 

Yoga & Pilates activities should be added to our devices, also the possibility to create a step by step workout for this profiles. Another feature should be the hydration widget. Dummy things for Garmin to be implemented in our devices. #odsweng

Why can I not use the Pilates workout type on my watch... 

That would defeat the purpose of use spending lots of money on a fancy watch that says it comes with preloaded works. And you also cannot find the same exercises in cardio as you can in pilates. 

Asking for this here is unlikely to have an effect. If you suggest it on the share ideas form, the more people who do that the better, more chance of it getting on the development roadmap, at least that's the idea.

And now I'm off to that page again myself to ask for my favorite activity: footbiking, with support for TWO cadence sensors. Although it's probably quicker to develop my own app or datafield for that - I've been asking for footbiking/kickbiking for years without result. No idea why apparently nobody else wants it. Footbikes are simply the best bikes; almost nothing to maintain, clean or repair, and a great workout. 

That would defeat the purpose of use spending lots of money on a fancy watch that says it comes with preloaded works.

I’ve been asking for Underwater Basketweaving for years too. It’s a growth sport in the small isolated village I live in the mountains but nearly everyone in my household participates. I agree. We pat hundreds of dollars for these watches and still they leave it highly popular sporting activities.

Garmin should have enabled every possible sport in the watches they supplied to ensure all customers are happy.

 Not even on the Descent MK2? Pilates it has.. but 1300 USD and no Underwater Basketweaving?

I get it that people have high expectations of expensive watches, but they can't have _everything_. The great thing about Garmin watches is lots of customization options, and with ConnectIQ you can accomplish a whole lot by building your own app.