Maybe just a decent 110 volt job would be the better option, you pay more and get less with cordless I find. As for Kapex, you pay even more just for the badge and green bits so nothing wrong with Bosch / Makita but I prefer Bosch.
I have a 240v Kapex in my workshop which I love but could do with something cordless for when I'm out of the shop. I nearly bought one of the Makita 18v ones as I have loads of batteries but then Makita released the 40v saw which does look good but I don't have any 40v batteries. Now Festool are releasing the cordless Kapex which I do have batteries for so do I wait for that? I know just how you feel.
I had a good look at the Makita at one of the Toolfairs and was surprised how compact it was, looked really portable, ideal for the van. The thing with the Festool would be you would never just chuck it in the van like you would the Makita, my Makita stuff doesn't get much love but I'm always a bit more careful with the Festool stuff.
If a portable and capable mitre saw fits for you then the Makita 40V should definitely be in your crosshairs. I've had mine almost a year now and it's proved to be extremely handy, plenty powerful, accurate and reliable.
My only gripe would be the dust port clogs up with no extraction. When you do stick an extractor on it, you have a moment wondering why you bothered and then the penny drops once again and you start digging out the port to clear the tubes.
A 2.5ah (effectively a 5ah 18V equivalent) battery has lasted me a day (sometimes 2) but then I'm not using it all day long. Compared to the 40V grinder (which you can measure runtime in blinks of an eye) I'd say it's pretty good on that front. BTW, the 40V charger is plenty quick... but has to be the noisiest charger of all time.