It`s the old story with those thickeners...they are only good/useful for a certain time, after that, you reach decision-time, on which path to choose.
To answer your question, thickeners have no adverse effect on system hair, no more than it does to growing hair.. however, it could possibly darken/stain your lace as it does on your pillow slips etc. You could simply order an extremely light-density blonde system and have Debbie colour it to match your own hair....I suggest blonde because that way, with such a light-density piece, knot-visibility would / could be an issue ..they`d need to be perfectly bleached. You could order a 2nd system at the same time with a stepped-up density and `wean` yourself [those around you at work ] up to the higher density after a few weeks...the fact that you are able to wear head-wear at work will be helpful.... you`d be surprised at how little notice people take of your hair generally.... certainly if you leave work on a Friday , literally bald on top, and arrive in on Monday with a full head of hair, there`ll be raised-eyebrows, but a gradual transition as I`ve suggested, while more expensive , due to ordering a number of systems with varying [upward] densities, will certainly `ease` the shock-factor.
Debbie has her own site http://www.splitendshairreplacement.com Contat details are on the site.