Uruguay is an interesting place. It seems to be a less modern and less developed version of next-door Argentina. Buenos Aires is a larger and more interesting city than Montevideo. There is a town there called Colonia, which is worth a couple days if you like old and charming cities. But most people who go to Uruguay either go to one of the posh beach resort towns (mainly Punta del Este), or they go to the tourist cattle ranches, which are surprisingly popular. If you haven’t been to Argentina yet you might find that it has more and different options, such as the Mendoza wine region and the mountain resort town of Bariloche.
If you are looking for beach weather in December then most of your list won’t work, and several of them are only on rivers. Starting from Kolkata you have many good choices that are much closer to you than anywhere in Europe or the Canary Islands, or the Caribbean for that matter. In fact, I’m a bit confused by your list because there are so many different types of places on it, many that aren’t warm or on beaches.
There is no better time than December to discover a still (somewhat) under-the-radar part of the Caribbean. This verdant, five square mile island has seen a lot of activity recently, from a new mega yacht club to a Soho House to the Mandarin Oriental's first property in the Caribbean. More is on the horizon for this picturesque piece of paradise, but go before everyone else discovers it.
Thank you very much Roger. I truly value your insight and am taking into consideration everything you’ve noted above. I’m going to check out the link you posted as well. That just reassured me that Bali would be great during that period. I’m thinking principally of staying in Ubud, Sanur or Seminyak for the type of trip I have in mind which is equal parts warm weather, walking/discovering, culture and some beach life. I’d love to visit Thailand but it’s just not the right time. At this point, I’m more intrigued by all of the many, still remote islands of Philippines than the chaotic lifestyle in Thailand. Perhaps, that’s just me still reeling from my trip to India a few months ago.
Even though November is one of the busy months in Pokhara, they've built so many new hotels in the past few years that finding a room – even at a decent price – should always be possible. The high-season rates are still very cheap by almost anyone else's standards, and food and drinks are always very affordable, but if you look around a bit you'll be able to do even better.
The Maldives could be great if you can afford it. December is the most expensive month there, at least the second half of December. There are about 100 private-island resorts there, and most of them have water villas that start at around US$400 per night and go WAY up from there. But island rooms are cheaper. I wouldn’t recommend going to Male or any of the other populated islands that have several smaller hotels. It’s just not the same experience that you get from the private-island resorts. I can help much more with this if you decide to go to the Maldives.
If you’re a bit more on the timid side, you can always use Yelp and TripAdvisor to get good insights on places people have visited. As a disclaimer, some of the ratings may not be accurate on these sites, so make sure you go through and read some of the more recent reviews that people have written. We did this for a few of the places we visited and had no issues.