Up until now I like the way the CMS functions, with templates, tidy and neat interface. That is, except the editor.
My need is for the most part a simple implementation for smaller websites with only one user who most often isn't skilled at using computers. I've made my own small cms, as I've experienced that small scale webhosting doesn't support heavy CMSes and often they confuse rather than ease the process for the end users. However, I kind of got tired of my end users being dependent upon me because of my custom made cms, so I decided to give third party open source CMSes a try. And OMG, the usual problems with every CMS having its faults became apparent once again.
I thought I had found something worthwhile with SilverStripe, however, the editor and its implementation is a serious setback, which I discovered after having installed and built a custom template. I have myself used tinymce often in my own small cms without problems, regularly upgrading as new builds came out.
In the stable alpha version it is partially incompatible with newer versions of chrome and explorer. In the beta version, the editor doesn't e.g. support tiny_mce_popup and I can't even edit the source code or make a custom image (to google maps).
Everything works, except the editor. The editor is at best quirky and at worst faulty. I could tell more about the faults, but frankly, it seems you have a long way to go here. I hope the alpha of v3 of SilverStripe remedies this.
Your implementation of tinymce doesn't seem to be that complex, but rather, for me, it would be more complex to look into your alterations and how your implementation is done rather than, perhaps, find some other solution to my CMS problem. Which is, of course, the usual problem using software someone else has developed.
Sorry about the sarcasm, but spending days cycling through implementing and configuring CMSes, just to discover they don't live up to expectations, kind of does this to you.
Very fine CMS, apart from this very important part of it - the part that the end user will most commonly use.
My advice is that you focus your efforts on the editor, because everything else doesn't really matter if it doesn't work properly. And keep it up to date as much as you possibly can.