I wish ODOT would just route 99E onto the Jefferson Highway. It is the historical route of 99E after all. I wish I had photos of it but for a few years in Jefferson city there were errorenous 99E route signs posted as part of a new traffic signal installation. They have all since been removed.
There's a business in Jefferson called something like "99 market," but that is a very old reference, since 99E has bypassed Jefferson since the 50's.
The biggest problem with making that highway 99E, IMO, would be that you'd have 99E leaving I-5 on the north end of the Jefferson Hwy, rejoining I-5 south of Jefferson, only to leave it again just a couple miles further south in Albany. Maybe BUS 99E would be more appropriate, but that seems silly for what's mostly a rural road. So maybe having its own designation of OR 164 works best. Mixed feelings on my part -- while I'd love to see recognition of a historic stretch of 99E, I can see the drawbacks of that.
The redesignation I'd like to see is BUS 99E in Salem. It doesn't actually connect to 99E on the north end, and its duplex with 22 on the south end just seems unnecessary. I understand the history of why ODOT pulled it off city-maintained Commercial St. on the south end when they moved the route designation from Portland Rd onto the Salem Parkway on the north end (bad blood between the agency and the city, as it was explained to me), but that would've actually been the routing that made sense. Now, I just think the Salem Parkway should have its own route number (probably OR 72, its hidden hwy #) and just end at OR 22 downtown. Either that, or make it an extension of OR 51, although that would also require a duplex with OR 22.
I couldn't find a secondary sign for Donald...unless it just isn't installed yet. I believe Newberg is listed on a secondary sign for at least northbound traffic (combined with Champoeg State Park); Newberg is also the control city listed for exit 294 (southbound) up in Tigard (however the BGSes on 217 omit Newberg and replace it with McMinnville...why the inconsistency? McMinnville doesn't even have any sign for northbound I-5 traffic; yet it's over 10,000 population larger than Newberg AND is the county seat of Yamhill County.)
Wow, that is inconsistent. It would be nice if they extended Ehlen Rd (which by this time has turned into McKay Rd) west to a new Willamette River crossing and tied it into OR 18 near Dayton to create a direct I-5-McMinnville connection, but I suppose the Newberg-Dundee Bypass would be close enough if it ever got built.
As far as Donald and other destinations, it's very likely more signage might be on the way. It looked to me that there was work about to start on erecting another advance BGS for either the Charbonneau or OR 551 exit (or both) just south of the Wilsonville bridge on I-5, for instance, so it's possible they might plan another for the Ehlen Rd exit, as well.
Sadly...even in downtown Salem, the signs for the Marion Street Bridge for OR 221 mention Dayton and not McMinnville. Granted Dayton is at the northern end of 221, but McMinnville is only 30 times larger than Dayton - and it's a much shorter distance to take 221/153/154 than to take 22 to Rickreall and then 99W.
Most traffic between Salem and McMinnville already takes the 221/153/154 routing, so people realize your point without the signage. I think the signs were just replaced as part of the repaving they're doing on 22, but I can't recall if the new signs mention McMinnville, either. I've always wondered why ODOT has yet to sign the latter 2 highways (153/154) when they're already being used so heavily for that regional traffic, but obviously the lack of state route signs hasn't hindered the use of those routes.