I'm considering investing in STR in Hawaii to diversify my investment portfolio (mainly for capital appreciation) as well as it being a regular vacation place for my family.

Generally there are multiple units for each "zone" if you will when I've seen them installed.Regarding your problem at hand, I personally would simply adjust your plan to move and make your initial plan to get the current issues resolved, while costly now, in the long run holding onto the unit will likely pay off. 

Investment Info:Single-family residence buy & hold investment.

If you plan to invest in multiple states or require advanced asset protection, consult a CPA or attorney to explore options like a holding company structure.

Is there really no way to hold shameless tenants accountable?

Ask an attorney for the cost breakdown, factor in holding costs, assume they'll do more damage on the way out and then ask for a bit more for the headache.But again, especially with no experience with evictions and it sounding like a mess, I would be very tempted to just walk if the tenant is not going to cooperate. 

The brokerage house can lend on margin for securities they hold. 

Due to time constraints (I was a graduate student), I've been holding all my investments passively in ETFs.

Play the long game and hold onto that equity. 

Otherwise, if you are referring to ETF's such as Spiders, or QQQ, the the holding period rules apply.