KYC/AML, custody, and payment gateway are the essentials. 

I work for a self-directed IRA custodian that specializes in alternative asset custody, and the majority of my day is spent talking to investors who are absolutely dumbfounded by the breadth of investment options, and that they have never heard of this before. 

@Scott RaleyIf you want to have a traditional custodian hold your alternative investment assets and want to do so inside a solo 401k plan instead of a SEP IRA, then IRA Services Trust Company can also help as they offer solo 401k plans and will custody the alternative assets such as real estate.

They know every judgement in court, they know who has custody, where the kids were registered in school etc.Do everyone a favor and stop trying to commit fraud.

I would imagine there is a way to remove someone "in abstencia", you can get a divorce, overturn custody, and adopt even without all parties involved if you can prove that a valid attempt was made so I would imagine there may be a way to clear title as well maybe not within 12 days but we'll see.

You can always go back to court for physical custody.

If you skip the LLC, your set up is only $350 and annual is $300, but there is a per transaction fee that would make this the more expensive option if you do over five transactions a year in the custodial model.  

@Daria B.since you are not self-employed and therefore do not qualify for a Solo 401k your choices are:1) self-directed custodial IRAor 2) Checkbook IRA (aka IRA LLC)While the first option give you the ability to have virtually limitless investment options you have to do so through a custodian.

Many Solo 401k advantages compared to the IRA come from the fact that there is no custodial requirement for the 401k.I confined my answer to the IRA and 401k structures.

@Bryan ScrivenerThe cost of establishing a LLC to be owned by your IRA should more than pay for itself in reduced custodial fees going forward.