There's a few local basketball leagues as competition (non-salaries), and they're more of a tournament than a league. None of them though do a combine or draft and even most semi-pro/"pro" teams/leagues don't even do combines or drafts (like the current ABA, IBL, PBL). I think it would be pretty hard/close to impossible to execute an exclusive combine&draft for your league when pretty much none of the other established leagues can do it and imo is due part to lack of interest/incentive(it just kinda doesn't work like that for low level pro leagues/semi pro). Pretty much every league I know of aside from the big leagues (NBA,NBADL,overseas) only scout & recruit on a low level. Venues would be highschools & community college gym's though.
It would be pretty difficult to sustain a local league that's "pro/semi-pro" in my opinion when the semi-pro/pro leagues that go around the country + the rest of North America are closing down due to lack of interest(from players and fans) and also when there's already many semi-pro teams in the area alone (across different leagues) that you have to compete with for talent and they pay.
Also, don't get confused with the "talent" that gets to the NBA/drafted and the talent in semi-pro/low level pro leagues, because they're completely different. I also feel like the amount of talent in Seattle is a little overstated, there's honestly not that much year in and year out. Someone might be a big recruit or go to the league every two or three years from Seattle, but it's obviously nothing like the talent in CA,NY,VA,FL,etc. where there are multiple guys every year going big. If anything it's more quality than quantity for Seattle. Recruiting good players to join your league is also pretty hard imo. Doesn't make sense for aged -18 players to join because PRO-AM/high school team is the way to go while you're in high school and aged 18-23ish is for colleges at all levels(D1,D2,JUCO,etc.). So your market for players is pretty much going to be 24/25+ year olds that are ex-college/nbad or good recreational hoopers. I just honestly don't know if the quality of play would be that good or if it'll just seem like a pick up game with people that have talent.
I'm not an expert or anything and this is just pretty much what I've seen/noticed being around some people and keeping up with bball for most of my life. My former HS coach (who still coaches at that school) is the current president/manager of Jamal Crawford's PRO-AM and also currently on the Seattle Mountaineers of the ABA & his dad is a pretty well known coach that is well affiliated with the the local NBA talent (coached many/most of them).