Assuming the logo itself is not up for discussion, I will say yes, you can use the r on its own.
I think example #3 is the best one.
- 1 gets a little convoluted.
- 2 is rather boring and generic.
I would also like to point out that 2 and 3 have "Lift" higher up and that works well. Lift - float - ascend etc., it emphasises the balloons (presumably) upwards motion, the direction you want your spirits to go :)
Yes; I think you can use the r, but do it with care. The reason I do not think it works well in #1 is partly because the context is missing a little... if the logo had been closer to the balloon/text, possibly in white-on-blue it would not look quite so bizarre jammed into the text like that. But to me it is a little "forced", and unnecessarily so.
It is a possibility that people will not instantly "get it", but I for one thinks that is not always a bad thing. A little intrigue, oddity makes for curious onlooker.
3 works best for me as it is a "freestanding" use of the r. It will then, eventually become an element of identity in itself independent of the logo, but that is in fact perfectly fine. I say go for it. Make the world a little more quirky.