Plugin questions

Ciao.
While working on an update of the halftime and doubletime plugins (see https://musescore.org/en/node/81641 ) I bumped into some issues:

1- I couldn't find a way to insert a rest at a cursor position which will read the cursor duration. For chords we can use cursor.addNote; is there an equivalent for rests? In the plugins I used the workaround of adding a note and then place the cursor at that position and read the duration of that note;

2- Is it possible to make operations with the FractionWrapper objects? For example, multiply the fraction by a constant, sum two fractions, divide two fractions, inside a plugin and obtain a FractionWrapper object (which is the one expected by the duration property of a chord/rest)?

3- I found a possible bug, see: https://musescore.org/en/node/92856 , when using the cursor.addNote function.

Are there possible answers to these questions, or is the plugin framework too limited (at the moment)?
Thank you for your help.

OS: Windows 8.1; MuseScore 2.0.2 & commit d08e14cc36

Ciao,
ABL