I would expect the 25 Ohms or even 100 Ohms to be still OK. It may effect the 10 MOhms input impedance ranges a little, but this would be higher than 10 V and usually the lower accuracy ranges anyway.
I would be more worried with leakage between the channels. So it may be a good idea to not use the very low resistance ones. At least unused channels should not contribute much to leakage. So the scanner may not be a good choice for high impedance source.
I added leakage current spec to my post. Seems the mos ones above at least are similar, for their max spec.
LCSC has some reed relays for ~$0.60, with better leakage (nA). But of course life is limited (10^8 cycles, about 3 years switching every second). There are also normal relays, and spec for the cheapies is really bad (~5uA, 10^5 life only!). Maybe some value in having a few reed and few photomos or similar.
One thing I'm not sure of, what is the purpose of channel 10 on the
original scan card? It uses K111 relay and U105 3301 photomos in series, with some 100R resistors. The other channels use a single relay.