<i>A sidenote on JIT:</i> I wrote the following while working out the structure of my post; I figured it wouldn&#x27;t hurt too much to post it too. The bulk of my question is above; what follows is more or less incidental.<p>I understand that JIT has something of a role in performance, and that modern Javascript engines couple the performance gains of JIT execution with a mind-boggling slew of different security and sandboxing techniques that aim to prevent unwanted data colliding with the CPU&#x27;s instruction pointer while still allowing near-C levels of performance. Thing is, what generally makes browsers&#x27; sometimes unbelievable JIT-powered performance[1] possible is the fact that the major JS engines - V8, JavaScriptCore, Chakra, Spidermonkey - have huge companies behind them that have the resources to fund continuous R&amp;D to iterate on performance while keeping abreast of security issues.<p>[1]: <a href="http:&#x2F;&#x2F;www.gopherjs.org&#x2F;blog&#x2F;2015&#x2F;09&#x2F;28&#x2F;surprises-in-gopherjs-performance&#x2F;" rel="nofollow">http:&#x2F;&#x2F;www.gopherjs.org&#x2F;blog&#x2F;2015&#x2F;09&#x2F;28&#x2F;surprises-in-gopherj...</a><p>But I&#x27;m not a browser manufacturer, or a computer science major (or even undergrad). I&#x27;m just a tinkerer who wants to play around with ideas that generally need safe remote code execution in a way that is transparent (to the extent a high-level competent end user could introspect all operations and control low-level settings) and trustable (for both the end user, who wants control of their device, and the developer, who wants a predictable environment).<p>I understand that JIT is generally incredibly hard to get right - this LuaJIT punchthrough[2] is an enlightening read (if just to learn what involved Lua code can look like :P) - and that once you flip the execute bit on any of the memory the OS has allocated it&#x27;s basically game on to start juggling how much to hypervise so performance doesn&#x27;t get hit too much.<p>[2]: <a href="http:&#x2F;&#x2F;www.corsix.org&#x2F;content&#x2F;malicious-luajit-bytecode" rel="nofollow">http:&#x2F;&#x2F;www.corsix.org&#x2F;content&#x2F;malicious-luajit-bytecode</a><p>The Web also has a mind-boggling churn rate, which can be offputting in some contexts&#x2F;situations that favor stability and consistency.