I'm confused about outsourcing? You mean with a CDN? Also, if you want bare minimum bootstrap, you can customize it and download it just like jQueryUI. Just download only what you need. Add to SMF install, no need to outsource, can be packaged with SMF. In any case, not my call. I just feel that maybe you are wasting valuable time on parts of a product (like Joshua already stated), for very little gain, when you could take advantage of open source code (Bootstrap modals, slideshows, tabs, etc.) that many have already discovered works flawlessly. This would allow your developers to focus on the very heart and soul of what SMF should be.
row
col-xs-{grid size part}
col-s-{grid size part}
col-md-{grid size part}
col-lg-{grid size part}
col-offset-md-{grid size part}
These are all classes that can make your job tons easier... and there's soooo many more!
For example:
<div class="row">
<div class="col-xs-24 col-md-12">Hello, I'm on Left Side in Large devices, and my own row in small devices.</div>
<div class="col-xs-24 col-md-12">Hello, I'm on Right Side in Large devices, and underneath previous div in small devices.</div>
</div>
"row" class automatically clears element. Many great looking sites built using bootstrap (
http://discoverphl.com ,
http://libertydiscountfuel.com ,
http://www.thinkitfirst.com just to name a few that I'm familiar with ). Why rebuild something that has been built with a solid foundation already? Because you don't want to rely on other 3rd party software? This is something you are already doing in SMF anyways. I seriously doubt CSS can cause a huge security risk as much as jQuery does. Many people I work with surprised that Forum software is even still around. SMF has a good chance at maintaining it, but new cutting-edge technologies are making Forum software not so much appealing anymore. Why is HTML 5 not implemented? Especially since HTML 5 has a huge advantage over 4, and has been around for quite some time now. Why is SMF just now starting to use jQuery after all of this time? How did it survive without it? Even moreso, how did it survive without responsive design for all of this time?
The only answer I can think of is, Good People, Good Core, and Good Support!