Can I get similar Full Text Search functionality without using Full-Text Search?
Native full-text can handle all of the features you've mentioned.


Ranking/relevance, weighting
Word inflection and expansion
Customisable noise words and thesaurus


Whether or not it will be the best solution for your particular domain is a tough call. Rather than attempt to hand-roll an alternative, spike a proof of concept using SQL FTS and repeat the exercise with one or more open source alternatives. 

Lucene is the obvious contender to compare and comes with the "Stack Overflow search is now 81% less crappy" endorsement of the SO team.