First, the gear we use, is safe to use for the purpose it is designed for.
The pic shows a config as a backup system while using a preset line. The line is not to be used as a means of access, but as a backupline while doing your walk/climb.
The purpose for the ascender with the handle is to use in a free upward way in a cave or on a rock, not in a tree with twigs and branches.
Recreational rock climbing can be done with quickdraws/biners without safety features on them like screw lock/tripple locking biners. That doesn't mean we should use them in our industry.
If we start to use stuff from other diciplines, we have to evaluate if those things are made for the purpose we want to give them.
In this case (the unmodified handled ascender) the arborists are dropping to the groud like leaves at the end of the season. Those things are not desighned for us arbo's in the twiggy treetops and even less if we climb thru the tree standing on branches (tilting the thing upside down).
Kong has modified it's ascenders for the use in this industry after numerous accidents.
Use that modified one or (I did not state the next line ;-)) modify your old one to the standard as they should be.