Stairrods now do a divider profile, I've been using a similar one primarily for mattwells, but also on the odd single step, it fits under the ply...
Quickstep lyvin do one similar to what i think you mean
I'm not certain, someone else will probably know better, but maybe cold weld
What is the depth of the stair tread? An undersized tread may cause you to kick the riser, every time you walk up the stairs. Having the stairs...
The festool ks60 is worth a look, if you fancy spending a bit more, it's as good as the ks120, just smaller, which makes it a bit more portable...
Just out of curiosity, which tools are you intending to buy?
So not worth recommending festool then,i used to have a dewalt, which was a nice mid range saw
What do you use it for? Don't say cutting wood lol
Most smaller flooring companies will provide the full service you require, the main difference will likely be, that they will be more transparent...