I can't find it but there was a poster that maintained near their original speed by 15 minutes of daily typing in Qwerty IIRC, but then 2 hours of practice in Colemak.   Their Colemak speed eventually surpassed their Qwerty speed. 

I think the order matters and helps explain why they were successful at this.  If you start daily refreshing a learned pattern you won't loose it. Then follow the reinforcement of something you know by practicing a new pattern followed by rest during which you give brain time for consolidation of the new learning, you are much more likely to efficiently learn the new pattern.   

I think your plan is going make it more difficult to learn Colemak than necessary.  It's a recipe for memory interference and goes counter to what we know about skill acquisition and memory retention.

I gave up with colemak,  dvorak just seemed easier and more comfortable, I'm now typing on it fairly quickly, though not qwerty speeds.  Something just felt right about dvorak this time I tried it.

I've been back on Colemak on and off for the past week and I've actually found it very easy to work with both layouts in the end. I've found that while Colemak works better for ordinary text, I have trouble with it when I'm programming -- mainly because when you're writing code, your hands go all over the place no matter what layout you're using. I'm now using the two almost interchangeably (though I'm still faster on qwerty at present).

My suggestion is to try a "qwerty by day, Colemak by night" approach. It worked quite well in my experience, and it avoids the risk of having your head bitten off by your boss in the early stages of learning when you are very slow. An hour of practice a day should get you up to speed on it surprisingly quickly.