Sorry - but I needed a while to think of that.
You should have no problem with that because isp_sieverules does not care about how managesieve is run. As far as I'm concerned also managesieve (run as a daemon) utilizes *.sieve files (or am I wrong here?).
So all isp_sieverules does is to catch the script BEFORE it is actually written and pass it on to ISPConfig. The via the api-functions it is integrated. So it does not matter if its a daemon or whatever. You should have not problems actually.