In your opinion, would it be a good idea to create a specialized online community for those involved in the hospitality service industry to exchange expertise? And what is the best platform to do so?

Of course, it's great idea! You may create Facebook community (page, group), blog (Wordpress), develop an application. Lot of opportunities.

There is so many community's like that. Just join them if you wish to learn. Check LinkedIn for instance, or airbnb.

Absolutely. There are several hospitality groups on LinkedIn which you can connect with to share ideas and expertise. 

Definitely yes, that would enlarge the experience of every individual  

Hello... there are many social specialized groups in the social media sites and many specialized blogs under this category... if you are planning to create your own site then you should advertise it targeting people working in this field... one of the ways is to advertise your site or group in similar blogs and social specialized groups.... but still to get your site or group more popular up to certain level you should then deal with it as a site and give more proper promotion... like google adwords... you should not forget paid promotion campaigns, now a days there is big big competition in this business

• It would definitely be a great idea and as such this can be done through many different platforms but the truth of the matter in my opinion is that the wider the reach you create the more engagement you get.
• LinkedIn offers you a ready database that you can use to create a group for like minded individuals, Facebook can do this as well but the focus might be a little different and so will other platforms.
• I would prefer forming a group on LinkedIn and / or supported by a blog with a similar focus.