What a fantastic breakdown of the concepts of POSSE vs. PESOS, though to be sure there are also additional variations for syndicating, cross-posting, or moving content around to reach various audiences.
One thing that I think you’ve only briefly touched upon is the ability to also have likes, replies/comments, etc. also come back to your site as native content via webmentions. I’ve been able to get rid of five apps and their incessant notifications and trim it all back to just using my own site to handle everything instead. Using something I choose to use instead of something I’m forced to, while also owning my data, is really very liberating.
Like you, I too have always wanted to own my own content on the web, and there are some easier and some harder methods. Not being as strong a developer as many, I’ve taken a more hybrid approach to things which is still evolving. To some extent I began at the easy end with some PESOS based workflows and relying on simple tools like IFTTT.com to at least begin owning all my content. For many content management systems, this is nearly dead easy, and could even be done with something as simple and flexible as Tumblr without much, if any, coding experience.
Over time, as I’ve been able, I’ve moved to a more direct POSSE method as either I or, more often, others have managed to master making the simple posting interfaces easier and easier. I think in the end, POSSE is the strongest of the methods, so that has always been my ultimate goal.
From a Drupal-centric approach, you might be able to gain an interesting perspective on the multitude of ways POSSE/PESOS can be done by looking at the various ways that are available in WordPress ecosystem. It’s probably easy to discern that some are far easier than others based on one’s facility with coding. In general, I’ve noticed that the more freedom and flexibility a particular method or plugin has, the longer it takes to code and/or configure. The less flexibility a plugin offers, the easier. (So one could compare something like SNAP at the more comprehensive/difficult end to something simpler like JetPack for POSSE.) The difficulty is in the administrative tax of keeping up with the panoply of social media platform APIs to keep things working smoothly over time, particularly when you want your posts to be able to leverage the broad arrays of posting options and display outputs platforms like Facebook and Twitter offer. The other difficult questions can sometimes be: am I just replacing one or two social platforms, or am I trying to replace 20? and am I doing them with one plugin or with 20? and finally, how DRY is that process? Sometimes manually cutting and pasting is just as good.
As you do, I write first and foremost for myself and then a distant second for reaction and conversation with others. Thus I think of my personal site as just that: personal. To some extent it’s a modern day version of a commonplace book where I collect a variety of thoughts in a variety of means, while still trying somewhat to keep it in an outer facing form to look what people might expect a site to look like. This means that I have a good number more than the traditional types of posts most social media sites have. I try to own all my own bookmarks and even post what I’m reading both online and in physical form. I keep highlights and annotations of things I find interesting. I naturally keep longer posts, status updates, and photos like many. I even log scrobbles of music and podcasts I listen to as well as film and television I watch. Interestingly there’s a tremendous amount I only publish privately to myself or a small circle of others that’s hidden on my site’s back end. Depending on how far and deep you want your experience to go you might want to consider how all these will look or be represented on your site. To a great extent, I think that WordPress’s attempt to copy Tumblr (text, photo, quote, link, chat, audio, video) with their Post Formats was interesting, it just didn’t go far enough. Naturally, this may take a different form for you depending on whether you’re building just for yourself or if you’re planning something more modular for the larger Drupal community to leverage.
The best part of all this is that I’ve not done any of it alone. While I try to maintain a list of some of my experiments to help others (you’ll probably appreciate the ones on mobile posting and RSS based on your outline), there’s also a wealth of other examples on the IndieWeb wiki and a terrifically stellar group of people around almost 24-7 in the IndieWeb chat to help spur me along. I’ll echo Tantek’s welcome to what I think is a more thoughtful and vibrant open web.
I hope others also find these resources so they’re not fumbling around in the dark as I was for so long. Since you’re obviously building in Drupal, I can recommend you take a look at some of the examples provided by the WordPress and the Known communities which Ben referenced. Since they’re all .php based and open-source, you may get further faster in addition to being able to iterate upon and improve their work. Many of the developers are frequently in the IndieWeb chat and I’m sure would be happy to help with ideas and pitfalls they came across along the way.
Like others, I’m posting my reply first on my own website, and manually cross-posting it to yours (manually until you support Webmention–perhaps via the Vinculum plugin?) as well as automatically to Twitter and others.