@ I know a few people who would write a new panel from scratch... for that kind of scratch... and really fast... me included... that's way too much money just to clean up the code.
The issue really isn't cleaning up the code. It is cleaning up the mess and having a real audit by a real firm that will back their work with certification / warranty / similar. Solus from a PR perspective is on the ropes about to get punched out. They need to get some pros on board to deal with media and how to help their customers going forward.
Solus can hire any hacks to modify the source to cover the low hanging issues. But I suspect being PHP, there are quite a few other exploits that are total control and unknown in public at this time - not per se PHP but how PHP is being used.
Audit needs to employ a team of programmers to deal with cleanup, as well a team of hacker types to exploit the software --- where they have full source to reverse engineer/come up with ideas from.
That's a big project with lots of folks involved. I suspect the $100-200k number might actually be low for a real audit/cleanup like this This would take, oh, months.
Sure, you can build a new panel for $100-200k. Still will be subject to breakage/exploits/etc. once it amasses any popularity. Still will probably end up doing this same was exploited, patch it, repeat and rinse dance.
Nothing stopping anyone from competing with SolusVM. Heck, from a business standpoint, the industry needs more paid software with actual support and backing. Look at the mess right now due to SolusVM stumbling like this. At least three exploits in a week... Where are providers going to go when Solus does a hatchet job and exploits continue next month? It's a very possible scenario.