Please suggest as I do not have an experience in OOTB features of excel online. We have sharepoint online and do not have access to central admin or dashboard designer.
Depending on your reports, there might not be any need to really do some frontend coding. If the reports are good as they are and you just need to display them on SP, it's fairly simple with Excel Web Access web part.
I assume you want to automate processes as much as possible?
Consider the following: In your Excel report you have a named area which shows the wanted information already. This could be done with e.g. Pivot tables. As reports are created, the plain data gets automatically updated to Pivot tables. In SharePoint you can use Excel Web Access wp to show the named area on your page.
report/dashboard that shows the team members availability
This really depends where you need to pull the data from. If it's from Outlook, Calendar is a good choice (consider also Gantt-view). If it's from Skype for Business, you can achieve the current availability with a plain list showing the user's presence. If it's from (manually?) created Excel, the above mentioned report displaying works for this as well.
- report/dashboard that shows the team members availability
In our farm we use list that have team members. Add a web part to page that shows this list and you are able to view the list of members on the page that will allow lync/skype status shown. You can modify the view of the web part to show exactly as you prefer.
- dashboard to show the incidents in pending, resolved or in progress state.
An InfoPath form viewer web part can be used to in lieu or instead of using excel web parts on a web page. The InfoPath can query data form the list or a ticketing system directly to include or summarize your data to your needs. Used this in past to summarize open tickets for the week, ticket Max days open, etc.
Why not generate the report and add it directly to a list? Either programmatically or by synching your spreadsheet see article. From there you will have more options. You can create custom views etc. and you could also use something like chart.js to generate graphs if required.
I've been building single page applications (Angular, JQuery, Yeoman) to interact with Sharepoint. I've gone so far as having javascript write Microsoft Word Templates that merge data pulled from Sharepoint as a solution for User Friendly Reporting. You should look at what you can do with CSOM. There's a couple of catches, if you host the single page application outside of sharepoint, you'll need update Sharepoint/IIS to return correct CORS header tags on the page requests. If you host the single page application within a Sharepoint Library folder, you'll need to re-configure some mimetypes like html, js, json to avoid them being blocked or treated as downloads vs page requests etc.
