A taxiway allows up to 100 tons.
Even the Boeing 707 weighs 116t w/o p****engers.
An Airbus A380 weighs up to 600 tons with p****engers!
(http://www.fast-function-factory.de/simutrans/simscr26.png)
Ahh, this, I am afraid, is a problem caused by Pak64 not being built with Simutrans-Experimental in mind. Given that Pak64 is open source, perhaps you can release an adapted version with correct taxiway weights?
I'd propose a 50t limit for older taxiways: that should allow only old planes and small jets to use it, as since jet-era planes are all over 70t empty (always based in real plane weights).
But IMHO, the best you can do is exporting all airplane info from the translator and load it in a spreadsheet. Then sort by weight and decide which ranges to use with each taxiway version. That should ease and shorten the process :)
Zeno makes sensible suggestions :-)